From 5ba21f4eb32ca00cffd3878d4ab93e97dd97375f Mon Sep 17 00:00:00 2001
From: ViperEkura <3081035982@qq.com>
Date: Mon, 27 Jul 2026 22:31:04 +0800
Subject: [PATCH] refactor: eliminate test duplication via shared helpers

- Add tests/helpers.py with shared config, dataset, tokenizer, executor, and assertion helpers
- Replace 15 copies of device one-liner with session-scoped fixture
- Collapse 5 near-identical Dataset subclasses into RandomTokenDataset
- Remove duplicate _make_config/_make_model/_make_frozen and FakeTokenizer/FakeExecutor definitions
- Make test_callbacks and test_early_stopping use existing train_config_factory
- Replace 6 duplicate meta.json read blocks with load_shard_meta
- Fix mkdtemp leaks in test_lora.py with TemporaryDirectory
---
 tests/conftest.py                      | 121 ++-------------
 tests/data/test_preprocess_pipeline.py |  30 +---
 tests/helpers.py                       | 207 +++++++++++++++++++++++++
 tests/inference/test_scheduler.py      |  49 ++----
 tests/module/test_encoder.py           |  66 +++-----
 tests/module/test_forward_configs.py   |  24 +--
 tests/module/test_lora.py              |  57 ++++---
 tests/module/test_tie_weight.py        |  49 +-----
 tests/trainer/conftest.py              |  51 +-----
 tests/trainer/test_callbacks.py        |  64 ++------
 tests/trainer/test_early_stopping.py   |  37 +----
 tests/trainer/test_grpo_strategy.py    |  61 +-------
 tests/trainer/test_online_e2e.py       |  16 +-
 tests/trainer/test_online_strategy.py  |  72 ++-------
 tests/trainer/test_rollout.py          |  80 +---------
 tests/trainer/test_signal_handler.py   |  41 +----
 16 files changed, 364 insertions(+), 661 deletions(-)
 create mode 100644 tests/helpers.py

diff --git a/tests/conftest.py b/tests/conftest.py
index 12ce6fe..be6abaa 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -6,11 +6,10 @@ import tempfile
 import pytest
 import torch
 from tokenizers import Tokenizer, models, pre_tokenizers, trainers
-from torch.utils.data import Dataset
 
-from astrai.config.model_config import AutoRegressiveLMConfig
 from astrai.model.transformer import AutoRegressiveLM
 from astrai.tokenize import AutoTokenizer
+from tests.helpers import TINY_CONFIG, RandomTokenDataset, make_tiny_config
 
 
 def pytest_configure(config):
@@ -19,6 +18,12 @@ def pytest_configure(config):
     config.addinivalue_line("markers", "unit: fast unit tests")
 
 
+@pytest.fixture(scope="session")
+def device():
+    """Session-scoped device string (``"cuda"`` if available, else ``"cpu"``)."""
+    return "cuda" if torch.cuda.is_available() else "cpu"
+
+
 def create_test_tokenizer(vocab_size: int = 1000) -> AutoTokenizer:
     """Create a simple tokenizer for testing purposes."""
     tokenizer = Tokenizer(models.BPE())
@@ -33,69 +38,6 @@ def create_test_tokenizer(vocab_size: int = 1000) -> AutoTokenizer:
     return auto_tokenizer
 
 
-class RandomDataset(Dataset):
-    """Random dataset for testing purposes."""
-
-    def __init__(self, length=None, max_length=64, vocab_size=1000):
-        self.length = length or int(torch.randint(100, 200, (1,)).item())
-        self.max_length = max_length
-        self.vocab_size = vocab_size
-
-    def __len__(self):
-        return self.length
-
-    def __getitem__(self, idx):
-        return {
-            "input_ids": torch.randint(0, self.vocab_size, (self.max_length,)),
-            "target_ids": torch.randint(0, self.vocab_size, (self.max_length,)),
-        }
-
-
-class MultiTurnDataset(Dataset):
-    """Multi-turn dataset with loss mask for SFT training tests."""
-
-    def __init__(self, length=None, max_length=64, vocab_size=1000):
-        self.length = length or int(torch.randint(100, 200, (1,)).item())
-        self.max_length = max_length
-        self.vocab_size = vocab_size
-
-    def __len__(self):
-        return self.length
-
-    def __getitem__(self, idx):
-        input_ids = torch.randint(0, self.vocab_size, (self.max_length,))
-        target_ids = torch.randint(0, self.vocab_size, (self.max_length,))
-        loss_mask = torch.randint(0, 1, (self.max_length,))
-
-        return {
-            "input_ids": input_ids,
-            "target_ids": target_ids,
-            "loss_mask": loss_mask,
-        }
-
-
-class EarlyStoppingDataset(Dataset):
-    """Dataset that triggers early stopping after consuming a specified number of samples."""
-
-    def __init__(self, length=10, stop_after=5):
-        self.length = length
-        self.stop_after = stop_after
-        self.count = 0
-
-    def __len__(self):
-        return self.length
-
-    def __getitem__(self, idx):
-        self.count += 1
-        if self.count == self.stop_after:
-            raise RuntimeError("Simulated early stopping")
-
-        return {
-            "input_ids": torch.randint(0, 1000, (64,)),
-            "target_ids": torch.randint(0, 1000, (64,)),
-        }
-
-
 @pytest.fixture(scope="session")
 def test_tokenizer():
     """Session-scoped tokenizer, created once for the entire test run."""
@@ -103,50 +45,20 @@ def test_tokenizer():
 
 
 @pytest.fixture(scope="session")
-def test_model():
+def test_model(device):
     """Session-scoped small AutoRegressiveLM model, created once."""
-    config = AutoRegressiveLMConfig(
-        vocab_size=1000,
-        hidden_size=8,
-        num_attention_heads=2,
-        num_key_value_heads=1,
-        intermediate_size=16,
-        max_position_embeddings=64,
-        num_hidden_layers=2,
-        rms_norm_eps=1e-5,
-    )
-    device = "cuda" if torch.cuda.is_available() else "cpu"
+    config = make_tiny_config()
     model = AutoRegressiveLM(config).to(device=device)
-
-    return {
-        "model": model,
-        "device": device,
-        "config": config,
-    }
+    return {"model": model, "device": device, "config": config}
 
 
 @pytest.fixture
 def base_test_env(test_model, test_tokenizer):
-    """Function-scoped test environment with isolated temp directory.
-
-    Composes session-scoped model and tokenizer with a per-test temp dir.
-    """
+    """Function-scoped test environment with isolated temp directory."""
     test_dir = tempfile.mkdtemp()
     config_path = os.path.join(test_dir, "config.json")
     with open(config_path, "w") as f:
-        json.dump(
-            {
-                "vocab_size": 1000,
-                "hidden_size": 8,
-                "num_attention_heads": 2,
-                "num_key_value_heads": 1,
-                "intermediate_size": 16,
-                "max_position_embeddings": 64,
-                "num_hidden_layers": 2,
-                "rms_norm_eps": 1e-5,
-            },
-            f,
-        )
+        json.dump(TINY_CONFIG, f)
 
     yield {
         "device": test_model["device"],
@@ -162,17 +74,14 @@ def base_test_env(test_model, test_tokenizer):
 
 @pytest.fixture
 def random_dataset():
-    dataset = RandomDataset()
-    yield dataset
+    return RandomTokenDataset(length=None)
 
 
 @pytest.fixture
 def multi_turn_dataset():
-    dataset = MultiTurnDataset()
-    yield dataset
+    return RandomTokenDataset(length=None, with_loss_mask=True)
 
 
 @pytest.fixture
 def early_stopping_dataset():
-    dataset = EarlyStoppingDataset()
-    yield dataset
+    return RandomTokenDataset(length=10, stop_after=5)
diff --git a/tests/data/test_preprocess_pipeline.py b/tests/data/test_preprocess_pipeline.py
index 90b7397..3857a79 100644
--- a/tests/data/test_preprocess_pipeline.py
+++ b/tests/data/test_preprocess_pipeline.py
@@ -16,6 +16,7 @@ from tests.data.conftest import (
     make_dpo_chat_config,
     make_grpo_no_template_config,
 )
+from tests.helpers import load_shard_meta
 
 
 def test_filter_by_length():
@@ -68,10 +69,7 @@ def test_full_chat_pipeline(temp_dir, chat_tokenizer_dir):
         tokenizer_path=chat_tokenizer_dir,
     ).run()
 
-    meta_path = os.path.join(out_dir, "__default__", "shard_0000", "meta.json")
-    assert os.path.exists(meta_path)
-    with open(meta_path, "r") as f:
-        meta = json.load(f)
+    meta = load_shard_meta(out_dir)
     assert "sequence" in meta
     assert "loss_mask" in meta
     assert meta["sequence"]["dtype"] == "int32"
@@ -112,10 +110,7 @@ def test_full_text_pipeline(temp_dir, tokenizer_dir):
         tokenizer_path=tokenizer_dir,
     ).run()
 
-    meta_path = os.path.join(out_dir, "__default__", "shard_0000", "meta.json")
-    assert os.path.exists(meta_path)
-    with open(meta_path, "r") as f:
-        meta = json.load(f)
+    meta = load_shard_meta(out_dir)
     assert "sequence" in meta
     assert "loss_mask" not in meta
 
@@ -158,10 +153,7 @@ def test_full_instruction_pipeline(temp_dir, tokenizer_dir):
         tokenizer_path=tokenizer_dir,
     ).run()
 
-    meta_path = os.path.join(out_dir, "__default__", "shard_0000", "meta.json")
-    assert os.path.exists(meta_path)
-    with open(meta_path, "r") as f:
-        meta = json.load(f)
+    meta = load_shard_meta(out_dir)
     assert "sequence" in meta
     assert "loss_mask" in meta
 
@@ -187,9 +179,7 @@ def test_dtype_override(temp_dir, tokenizer_dir):
         tokenizer_path=tokenizer_dir,
     ).run()
 
-    meta_path = os.path.join(out_dir, "__default__", "shard_0000", "meta.json")
-    with open(meta_path, "r") as f:
-        meta = json.load(f)
+    meta = load_shard_meta(out_dir)
     assert meta["sequence"]["dtype"] == "int32"
     assert meta["loss_mask"]["dtype"] == "bool"
 
@@ -221,10 +211,7 @@ def test_dpo_pipeline(temp_dir, chat_tokenizer_dir):
         tokenizer_path=chat_tokenizer_dir,
     ).run()
 
-    meta_path = os.path.join(out_dir, "__default__", "shard_0000", "meta.json")
-    assert os.path.exists(meta_path)
-    with open(meta_path, "r") as f:
-        meta = json.load(f)
+    meta = load_shard_meta(out_dir)
     assert "chosen" in meta
     assert "rejected" in meta
     assert "chosen_mask" in meta
@@ -254,10 +241,7 @@ def test_grpo_pipeline(temp_dir, tokenizer_dir):
         tokenizer_path=tokenizer_dir,
     ).run()
 
-    meta_path = os.path.join(out_dir, "__default__", "shard_0000", "meta.json")
-    assert os.path.exists(meta_path)
-    with open(meta_path, "r") as f:
-        meta = json.load(f)
+    meta = load_shard_meta(out_dir)
     assert "prompts" in meta
     assert "responses" in meta
     assert "masks" in meta
diff --git a/tests/helpers.py b/tests/helpers.py
new file mode 100644
index 0000000..17c4428
--- /dev/null
+++ b/tests/helpers.py
@@ -0,0 +1,207 @@
+"""Shared test helpers for the AstrAI test suite."""
+
+import json
+import os
+
+import torch
+from torch.utils.data import Dataset
+
+from astrai.config.model_config import AutoRegressiveLMConfig
+from astrai.model.transformer import AutoRegressiveLM
+
+TINY_CONFIG = dict(
+    vocab_size=1000,
+    hidden_size=8,
+    num_attention_heads=2,
+    num_key_value_heads=1,
+    intermediate_size=16,
+    max_position_embeddings=64,
+    num_hidden_layers=2,
+    rms_norm_eps=1e-5,
+)
+
+CHAT_TEMPLATE = (
+    "{% for message in messages %}"
+    "{% if message['role'] == 'system' %}SYSTEM: {{ message['content'] }}\n{% endif %}"
+    "{% if message['role'] == 'user' %}USER: {{ message['content'] }}\n{% endif %}"
+    "{% if message['role'] == 'assistant' %}ASSISTANT: {{ message['content'] }}\n{% endif %}"
+    "{% endfor %}"
+    "{% if add_generation_prompt %}ASSISTANT: {% endif %}"
+)
+
+
+def make_tiny_config(**overrides):
+    """Create a tiny ``AutoRegressiveLMConfig`` for tests.
+
+    All keyword arguments override ``TINY_CONFIG`` defaults.
+    """
+    return AutoRegressiveLMConfig(**{**TINY_CONFIG, **overrides})
+
+
+def make_rollout_config(vocab_size=200, max_position_embeddings=64, **kwargs):
+    """Create a tiny config sized for rollout / strategy tests."""
+    return make_tiny_config(
+        vocab_size=vocab_size,
+        hidden_size=16,
+        intermediate_size=32,
+        max_position_embeddings=max_position_embeddings,
+        **kwargs,
+    )
+
+
+def make_model(device, **cfg_overrides):
+    """Create a tiny ``AutoRegressiveLM`` on *device* and return ``(model, config)``."""
+    cfg = make_rollout_config(**cfg_overrides)
+    model = AutoRegressiveLM(cfg).to(device=device)
+    model.eval()
+    return model, cfg
+
+
+def make_frozen(model, device):
+    """Create a frozen, eval-mode copy of *model* with identical weights."""
+    cfg = make_rollout_config()
+    copy = AutoRegressiveLM(cfg).to(device=device)
+    copy.load_state_dict(model.state_dict())
+    copy.requires_grad_(False)
+    copy.eval()
+    return copy
+
+
+class RandomTokenDataset(Dataset):
+    """Random token dataset combining all test dataset variants.
+
+    Parameters
+    ----------
+    length : int or None
+        Fixed length, or ``None`` for a random length in [100, 200).
+    max_length : int
+        Sequence length per sample.
+    vocab_size : int
+        Upper bound for random token ids.
+    with_loss_mask : bool
+        Include a ``loss_mask`` key in each sample.
+    stop_after : int or None
+        Raise ``RuntimeError`` after this many samples (for early-stopping tests).
+    """
+
+    def __init__(
+        self,
+        length=100,
+        max_length=64,
+        vocab_size=1000,
+        *,
+        with_loss_mask=False,
+        stop_after=None,
+    ):
+        self.length = (
+            length if length is not None else int(torch.randint(100, 200, (1,)).item())
+        )
+        self.max_length = max_length
+        self.vocab_size = vocab_size
+        self.with_loss_mask = with_loss_mask
+        self.stop_after = stop_after
+        self._count = 0
+
+    def __len__(self):
+        return self.length
+
+    def __getitem__(self, idx):
+        if self.stop_after is not None:
+            self._count += 1
+            if self._count == self.stop_after:
+                raise RuntimeError("Simulated early stopping")
+
+        item = {
+            "input_ids": torch.randint(0, self.vocab_size, (self.max_length,)),
+            "target_ids": torch.randint(0, self.vocab_size, (self.max_length,)),
+        }
+        if self.with_loss_mask:
+            item["loss_mask"] = torch.randint(0, 1, (self.max_length,))
+        return item
+
+
+class FakeTokenizer:
+    """Minimal stub tokenizer with optional chat-template support."""
+
+    stop_ids = [2]
+
+    def __init__(self, *, with_chat_template=False):
+        if with_chat_template:
+            from astrai.tokenize.chat_template import ChatTemplate
+
+            self._chat_template = ChatTemplate.from_string(CHAT_TEMPLATE)
+        else:
+            self._chat_template = None
+
+    def encode(self, texts, **_):
+        if isinstance(texts, str):
+            texts = [texts]
+        return [[b for b in t.encode("utf-8")] for t in texts]
+
+    def decode(self, ids, skip_special_tokens=True):
+        if isinstance(ids, list):
+            return bytes(b for b in ids if b > 2 or not skip_special_tokens).decode(
+                "utf-8", errors="ignore"
+            )
+        return str(ids)
+
+    def apply_chat_template(
+        self, messages, tokenize=True, add_generation_prompt=True, **_
+    ):
+        if self._chat_template is None:
+            raise RuntimeError("Chat template not configured")
+        rendered = self._chat_template.render(
+            messages=messages, add_generation_prompt=add_generation_prompt
+        )
+        if tokenize:
+            return (
+                self.encode(rendered)[0]
+                if isinstance(rendered, str)
+                else [self.encode(t)[0] for t in rendered]
+            )
+        return rendered
+
+
+class FakeExecutor:
+    """Executor stub tracking ``sync_gradients`` and providing ``unwrap_model``."""
+
+    def __init__(self, sync_gradients=True):
+        self._sync_gradients = sync_gradients
+
+    @property
+    def sync_gradients(self):
+        return self._sync_gradients
+
+    def unwrap_model(self, model):
+        return model.state_dict()
+
+
+def find_checkpoint_meta(ckpt_dir):
+    """Walk *ckpt_dir* and return the path to the first ``meta.json`` found."""
+    for root, _dirs, files in os.walk(ckpt_dir):
+        if "meta.json" in files:
+            return os.path.join(root, "meta.json")
+    return None
+
+
+def load_checkpoint_meta(ckpt_dir):
+    """Find and load the first checkpoint ``meta.json`` under *ckpt_dir*."""
+    meta_path = find_checkpoint_meta(ckpt_dir)
+    assert meta_path is not None, f"No checkpoint meta.json found in {ckpt_dir}"
+    with open(meta_path) as f:
+        return json.load(f)
+
+
+def load_shard_meta(out_dir):
+    """Load ``meta.json`` from the default shard output directory."""
+    meta_path = os.path.join(out_dir, "__default__", "shard_0000", "meta.json")
+    assert os.path.exists(meta_path), f"Shard meta.json not found at {meta_path}"
+    with open(meta_path) as f:
+        return json.load(f)
+
+
+def assert_state_dicts_equal(a, b):
+    """Assert two state dicts have identical keys and equal tensor values."""
+    assert set(a.keys()) == set(b.keys()), f"Key mismatch: {set(a) ^ set(b)}"
+    for key in a:
+        assert torch.equal(a[key], b[key]), f"Tensor mismatch at key: {key}"
diff --git a/tests/inference/test_scheduler.py b/tests/inference/test_scheduler.py
index 9ed9b29..2475176 100644
--- a/tests/inference/test_scheduler.py
+++ b/tests/inference/test_scheduler.py
@@ -7,6 +7,8 @@ import pytest
 import torch
 
 from astrai.inference import InferenceScheduler
+from astrai.model.transformer import AutoRegressiveLM
+from tests.helpers import FakeTokenizer, make_rollout_config
 
 
 @pytest.fixture
@@ -195,34 +197,9 @@ def test_prefill_skips_fully_cached_tasks(mock_model_and_tokenizer):
 
 def _make_real_scheduler(device):
     """Build a scheduler backed by a tiny real model for run_batch tests."""
-    from astrai.config.model_config import AutoRegressiveLMConfig
-    from astrai.model.transformer import AutoRegressiveLM
-
-    class _Tok:
-        stop_ids = [2]
-
-        def encode(self, texts, **_):
-            if isinstance(texts, str):
-                texts = [texts]
-            return [[b for b in t.encode("utf-8")] for t in texts]
-
-        def decode(self, ids, skip_special_tokens=True):
-            return bytes(b for b in ids if b > 2 or not skip_special_tokens).decode(
-                "utf-8", errors="ignore"
-            )
-
-    cfg = AutoRegressiveLMConfig(
-        vocab_size=200,
-        hidden_size=16,
-        num_attention_heads=2,
-        num_key_value_heads=1,
-        intermediate_size=32,
-        max_position_embeddings=64,
-        num_hidden_layers=2,
-        rms_norm_eps=1e-5,
-    )
+    cfg = make_rollout_config(max_position_embeddings=64)
     model = AutoRegressiveLM(cfg).to(device=device).eval()
-    tokenizer = _Tok()
+    tokenizer = FakeTokenizer()
     scheduler = InferenceScheduler(
         model=model,
         tokenizer=tokenizer,
@@ -232,8 +209,7 @@ def _make_real_scheduler(device):
     return scheduler, tokenizer, model
 
 
-def test_run_batch_returns_token_sequences():
-    device = "cuda" if torch.cuda.is_available() else "cpu"
+def test_run_batch_returns_token_sequences(device):
     scheduler, _tok, _model = _make_real_scheduler(device)
     try:
         prompts = [[10, 20, 30], [5, 6, 7, 8]]
@@ -247,9 +223,8 @@ def test_run_batch_returns_token_sequences():
         scheduler.stop()
 
 
-def test_run_batch_return_logprobs_aligned():
+def test_run_batch_return_logprobs_aligned(device):
     """return_logprobs=True gives (token_ids, logprobs) tuples with equal len."""
-    device = "cuda" if torch.cuda.is_available() else "cpu"
     scheduler, _tok, _model = _make_real_scheduler(device)
     try:
         prompts = [[10, 20, 30, 40]]
@@ -264,8 +239,7 @@ def test_run_batch_return_logprobs_aligned():
         scheduler.stop()
 
 
-def test_run_batch_respects_max_tokens():
-    device = "cuda" if torch.cuda.is_available() else "cpu"
+def test_run_batch_respects_max_tokens(device):
     scheduler, _tok, _model = _make_real_scheduler(device)
     try:
         prompts = [[10, 20, 30]]
@@ -275,9 +249,8 @@ def test_run_batch_respects_max_tokens():
         scheduler.stop()
 
 
-def test_run_batch_stop_id_terminates():
+def test_run_batch_stop_id_terminates(device):
     """A token matching stop_ids terminates generation for that prompt."""
-    device = "cuda" if torch.cuda.is_available() else "cpu"
     scheduler, _tok, _model = _make_real_scheduler(device)
     try:
         prompts = [[10, 20, 30]]
@@ -290,9 +263,8 @@ def test_run_batch_stop_id_terminates():
         scheduler.stop()
 
 
-def test_run_batch_empty_prompts():
+def test_run_batch_empty_prompts(device):
     """Empty prompt list yields empty result list."""
-    device = "cuda" if torch.cuda.is_available() else "cpu"
     scheduler, _tok, _model = _make_real_scheduler(device)
     try:
         assert scheduler.run_batch([], max_tokens=4) == []
@@ -300,9 +272,8 @@ def test_run_batch_empty_prompts():
         scheduler.stop()
 
 
-def test_run_batch_too_long_prompt_skipped():
+def test_run_batch_too_long_prompt_skipped(device):
     """A prompt longer than max_seq_len yields an empty result slot."""
-    device = "cuda" if torch.cuda.is_available() else "cpu"
     scheduler, _tok, _model = _make_real_scheduler(device)
     try:
         long = list(range(100))  # > max_seq_len=64
diff --git a/tests/module/test_encoder.py b/tests/module/test_encoder.py
index 1af7b85..3b3b0a9 100644
--- a/tests/module/test_encoder.py
+++ b/tests/module/test_encoder.py
@@ -9,34 +9,22 @@ import torch
 from astrai.config.model_config import EncoderConfig
 from astrai.model.automodel import AutoModel
 from astrai.model.encoder import EmbeddingEncoder
-
-TINY_CONFIG = dict(
-    vocab_size=128,
-    hidden_size=8,
-    num_attention_heads=2,
-    num_key_value_heads=1,
-    intermediate_size=16,
-    max_position_embeddings=64,
-    num_hidden_layers=2,
-    rms_norm_eps=1e-5,
-)
-
-_device = "cuda" if torch.cuda.is_available() else "cpu"
+from tests.helpers import TINY_CONFIG, assert_state_dicts_equal
 
 
-def _make_model(**kwargs):
+def _make_model(device, **kwargs):
     config = EncoderConfig(**{**TINY_CONFIG, **kwargs})
-    return EmbeddingEncoder(config).to(device=_device)
+    return EmbeddingEncoder(config).to(device=device)
 
 
 @pytest.mark.parametrize("pooling_type", ["mean", "cls", "last"])
-def test_encoder_forward_pooling(pooling_type):
-    model = _make_model(pooling_type=pooling_type)
+def test_encoder_forward_pooling(pooling_type, device):
+    model = _make_model(device, pooling_type=pooling_type)
     model.eval()
 
     batch_size, seq_len = 2, 8
     input_ids = torch.randint(
-        0, TINY_CONFIG["vocab_size"], (batch_size, seq_len), device=_device
+        0, TINY_CONFIG["vocab_size"], (batch_size, seq_len), device=device
     )
 
     with torch.no_grad():
@@ -46,15 +34,15 @@ def test_encoder_forward_pooling(pooling_type):
     assert not torch.isnan(output).any()
 
 
-def test_encoder_forward_with_padding():
-    model = _make_model()
+def test_encoder_forward_with_padding(device):
+    model = _make_model(device)
     model.eval()
 
     batch_size, seq_len = 2, 8
     input_ids = torch.randint(
-        0, TINY_CONFIG["vocab_size"], (batch_size, seq_len), device=_device
+        0, TINY_CONFIG["vocab_size"], (batch_size, seq_len), device=device
     )
-    input_mask = torch.ones(batch_size, seq_len, dtype=torch.bool, device=_device)
+    input_mask = torch.ones(batch_size, seq_len, dtype=torch.bool, device=device)
     input_mask[:, 4:] = False
 
     with torch.no_grad():
@@ -64,13 +52,13 @@ def test_encoder_forward_with_padding():
     assert not torch.isnan(output).any()
 
 
-def test_encoder_normalize():
-    model = _make_model(pooling_type="mean", normalize_embeddings=True)
+def test_encoder_normalize(device):
+    model = _make_model(device, pooling_type="mean", normalize_embeddings=True)
     model.eval()
 
     batch_size, seq_len = 2, 8
     input_ids = torch.randint(
-        0, TINY_CONFIG["vocab_size"], (batch_size, seq_len), device=_device
+        0, TINY_CONFIG["vocab_size"], (batch_size, seq_len), device=device
     )
 
     with torch.no_grad():
@@ -86,26 +74,24 @@ def test_encoder_register():
     assert cls is EmbeddingEncoder
 
 
-def test_encoder_from_transformer_checkpoint():
-    model = _make_model()
+def test_encoder_from_transformer_checkpoint(device):
+    model = _make_model(device)
     state_dict = model.state_dict()
     state_dict["lm_head.weight"] = torch.randn(
-        TINY_CONFIG["vocab_size"], TINY_CONFIG["hidden_size"], device=_device
+        TINY_CONFIG["vocab_size"], TINY_CONFIG["hidden_size"], device=device
     )
 
-    new_model = _make_model()
+    new_model = _make_model(device)
     new_model.load_state_dict(state_dict, strict=True)
 
-    for key in model.state_dict():
-        assert torch.equal(new_model.state_dict()[key], model.state_dict()[key])
+    assert_state_dicts_equal(new_model.state_dict(), model.state_dict())
 
 
-def test_encoder_save_load():
-    test_dir = tempfile.mkdtemp(prefix="encoder_test_")
-    config_path = os.path.join(test_dir, "config.json")
-    weights_path = os.path.join(test_dir, "model.safetensors")
+def test_encoder_save_load(device):
+    with tempfile.TemporaryDirectory(prefix="encoder_test_") as test_dir:
+        config_path = os.path.join(test_dir, "config.json")
+        weights_path = os.path.join(test_dir, "model.safetensors")
 
-    try:
         config_data = {**TINY_CONFIG, "pooling_type": "mean"}
         with open(config_path, "w") as f:
             json.dump(config_data, f)
@@ -117,10 +103,4 @@ def test_encoder_save_load():
         loaded = EmbeddingEncoder(config)
         loaded.load_state_dict(st.load_file(weights_path))
 
-        for key in original.state_dict():
-            assert torch.equal(original.state_dict()[key], loaded.state_dict()[key])
-    finally:
-        if os.path.exists(test_dir):
-            for f in os.listdir(test_dir):
-                os.remove(os.path.join(test_dir, f))
-            os.rmdir(test_dir)
+        assert_state_dicts_equal(original.state_dict(), loaded.state_dict())
diff --git a/tests/module/test_forward_configs.py b/tests/module/test_forward_configs.py
index da00c32..d659a82 100644
--- a/tests/module/test_forward_configs.py
+++ b/tests/module/test_forward_configs.py
@@ -1,20 +1,8 @@
 import pytest
 import torch
 
-from astrai.config.model_config import AutoRegressiveLMConfig
 from astrai.model.transformer import AutoRegressiveLM
-
-TINY_CONFIG = dict(
-    vocab_size=128,
-    hidden_size=8,
-    num_attention_heads=2,
-    num_key_value_heads=1,
-    intermediate_size=16,
-    max_position_embeddings=64,
-    num_hidden_layers=2,
-    rms_norm_eps=1e-5,
-)
-
+from tests.helpers import TINY_CONFIG
 
 CONFIGS = [
     pytest.param(
@@ -70,9 +58,10 @@ CONFIGS = [
 
 
 @pytest.mark.parametrize("config_kwargs", CONFIGS)
-def test_model_forward(config_kwargs):
+def test_model_forward(config_kwargs, device):
+    from astrai.config.model_config import AutoRegressiveLMConfig
+
     config = AutoRegressiveLMConfig(**config_kwargs)
-    device = "cuda" if torch.cuda.is_available() else "cpu"
     model = AutoRegressiveLM(config).to(device=device)
     model.eval()
 
@@ -97,9 +86,10 @@ def test_model_forward(config_kwargs):
 
 
 @pytest.mark.parametrize("config_kwargs", CONFIGS)
-def test_model_forward_with_padding(config_kwargs):
+def test_model_forward_with_padding(config_kwargs, device):
+    from astrai.config.model_config import AutoRegressiveLMConfig
+
     config = AutoRegressiveLMConfig(**config_kwargs)
-    device = "cuda" if torch.cuda.is_available() else "cpu"
     model = AutoRegressiveLM(config).to(device=device)
     model.eval()
 
diff --git a/tests/module/test_lora.py b/tests/module/test_lora.py
index 0a89a41..d95a397 100644
--- a/tests/module/test_lora.py
+++ b/tests/module/test_lora.py
@@ -249,17 +249,17 @@ def test_save_load_roundtrip():
     with torch.no_grad():
         out_src = model(x)["logits"].clone()
 
-    tmpdir = tempfile.mkdtemp()
-    save_lora(model, tmpdir, cfg)
+    with tempfile.TemporaryDirectory() as tmpdir:
+        save_lora(model, tmpdir, cfg)
 
-    model2 = _make_model()
-    model2.load_state_dict(model.state_dict(), strict=False)
-    load_lora(model2, tmpdir)
+        model2 = _make_model()
+        model2.load_state_dict(model.state_dict(), strict=False)
+        load_lora(model2, tmpdir)
 
-    with torch.no_grad():
-        out_dst = model2(x)["logits"]
+        with torch.no_grad():
+            out_dst = model2(x)["logits"]
 
-    torch.testing.assert_close(out_src, out_dst)
+        torch.testing.assert_close(out_src, out_dst)
 
 
 def test_save_after_merge_raises():
@@ -271,13 +271,13 @@ def test_save_after_merge_raises():
             if isinstance(m, LoRALinear):
                 m.lora_B.fill_(0.5)
 
-    tmpdir = tempfile.mkdtemp()
-    save_lora(model, tmpdir, cfg)
-    merge_lora(model)
+    with tempfile.TemporaryDirectory() as tmpdir:
+        save_lora(model, tmpdir, cfg)
+        merge_lora(model)
 
-    tmpdir2 = tempfile.mkdtemp()
-    with pytest.raises(RuntimeError, match="No LoRA parameters"):
-        save_lora(model, tmpdir2, cfg)
+        with tempfile.TemporaryDirectory() as tmpdir2:
+            with pytest.raises(RuntimeError, match="No LoRA parameters"):
+                save_lora(model, tmpdir2, cfg)
 
 
 def test_load_lora_on_already_injected():
@@ -289,16 +289,15 @@ def test_load_lora_on_already_injected():
             if isinstance(m, LoRALinear):
                 m.lora_B.fill_(0.5)
 
-    tmpdir = tempfile.mkdtemp()
-    save_lora(model, tmpdir, LoRAConfig(r=4, alpha=8, target_modules=("q_proj",)))
+    with tempfile.TemporaryDirectory() as tmpdir:
+        save_lora(model, tmpdir, LoRAConfig(r=4, alpha=8, target_modules=("q_proj",)))
 
-    model2 = _make_model()
-    model2.load_state_dict(model.state_dict(), strict=False)
-    inject_lora(model2, r=4, alpha=8, target_modules={"q_proj"})
+        model2 = _make_model()
+        model2.load_state_dict(model.state_dict(), strict=False)
+        inject_lora(model2, r=4, alpha=8, target_modules={"q_proj"})
 
-    # load onto already-injected model
-    load_lora(model2, tmpdir)
-    assert _get_lora_count(model2) > 0
+        load_lora(model2, tmpdir)
+        assert _get_lora_count(model2) > 0
 
 
 def test_load_lora_mismatched_r_raises():
@@ -310,15 +309,15 @@ def test_load_lora_mismatched_r_raises():
             if isinstance(m, LoRALinear):
                 m.lora_B.fill_(0.5)
 
-    tmpdir = tempfile.mkdtemp()
-    save_lora(model, tmpdir, cfg)
+    with tempfile.TemporaryDirectory() as tmpdir:
+        save_lora(model, tmpdir, cfg)
 
-    model2 = _make_model()
-    model2.load_state_dict(model.state_dict(), strict=False)
-    inject_lora(model2, r=4, alpha=8, target_modules={"q_proj"})
+        model2 = _make_model()
+        model2.load_state_dict(model.state_dict(), strict=False)
+        inject_lora(model2, r=4, alpha=8, target_modules={"q_proj"})
 
-    with pytest.raises(RuntimeError, match="size mismatch"):
-        load_lora(model2, tmpdir)  # strict=False, only lora keys
+        with pytest.raises(RuntimeError, match="size mismatch"):
+            load_lora(model2, tmpdir)
 
 
 def test_merge_preserves_output():
diff --git a/tests/module/test_tie_weight.py b/tests/module/test_tie_weight.py
index d60ed7b..e495b13 100644
--- a/tests/module/test_tie_weight.py
+++ b/tests/module/test_tie_weight.py
@@ -1,6 +1,5 @@
 import json
 import os
-import tempfile
 
 import pytest
 import safetensors.torch as st
@@ -8,43 +7,13 @@ import torch
 
 from astrai.config.model_config import AutoRegressiveLMConfig
 from astrai.model.transformer import AutoRegressiveLM
+from tests.helpers import TINY_CONFIG
 
 
-@pytest.fixture
-def transformer_test_env():
-    test_dir = tempfile.mkdtemp(prefix="transformer_test_")
-    config_path = os.path.join(test_dir, "config.json")
+def test_tie_weight_init(base_test_env):
+    config_path = base_test_env["config_path"]
 
-    config = {
-        "vocab_size": 1000,
-        "hidden_size": 8,
-        "num_attention_heads": 2,
-        "num_key_value_heads": 1,
-        "intermediate_size": 16,
-        "max_position_embeddings": 64,
-        "num_hidden_layers": 2,
-        "rms_norm_eps": 1e-5,
-    }
-
-    with open(config_path, "w") as f:
-        json.dump(config, f)
-
-    yield {"test_dir": test_dir, "config_path": config_path, "config": config}
-
-    if os.path.exists(test_dir):
-        try:
-            for file in os.listdir(test_dir):
-                os.remove(os.path.join(test_dir, file))
-            os.rmdir(test_dir)
-        except Exception:
-            pass
-
-
-def test_tie_weight_init(transformer_test_env):
-    config_path = transformer_test_env["config_path"]
-    config_data = transformer_test_env["config"].copy()
-
-    # case 1: tie weight
+    config_data = TINY_CONFIG.copy()
     config_data["tie_word_embeddings"] = True
 
     with open(config_path, "w") as f:
@@ -62,7 +31,6 @@ def test_tie_weight_init(transformer_test_env):
     assert torch.equal(model.lm_head.weight, model.embed_tokens.weight)
     assert not torch.equal(model.lm_head.weight, original_weight)
 
-    # case 2: not tie weight
     config_data["tie_word_embeddings"] = False
 
     with open(config_path, "w") as f:
@@ -81,13 +49,11 @@ def test_tie_weight_init(transformer_test_env):
     assert not torch.equal(model.lm_head.weight, original_weight)
 
 
-def test_model_save_load_with_tie_weight(transformer_test_env):
-    test_dir = transformer_test_env["test_dir"]
+def test_model_save_load_with_tie_weight(base_test_env):
+    test_dir = base_test_env["test_dir"]
     model_path = os.path.join(test_dir, "model.safetensors")
 
-    config_data = transformer_test_env["config"].copy()
-
-    # case 1: tie weight
+    config_data = TINY_CONFIG.copy()
     config_data["tie_word_embeddings"] = True
     config_path = os.path.join(test_dir, "config.json")
 
@@ -107,7 +73,6 @@ def test_model_save_load_with_tie_weight(transformer_test_env):
     assert model.lm_head.weight.data_ptr() == model.embed_tokens.weight.data_ptr()
     assert "lm_head.weight" not in model.state_dict()
 
-    # case 2: not tie weight (form tie-weight state dict load)
     config_data["tie_word_embeddings"] = False
     with open(config_path, "w") as f:
         json.dump(config_data, f)
diff --git a/tests/trainer/conftest.py b/tests/trainer/conftest.py
index bc02316..87b1cc4 100644
--- a/tests/trainer/conftest.py
+++ b/tests/trainer/conftest.py
@@ -2,33 +2,15 @@ import os
 
 import pytest
 import torch
-from torch.utils.data import Dataset
 
 from astrai.config import TrainConfig
 from astrai.trainer.schedule import SchedulerFactory
-
-
-class TrainerDataset(Dataset):
-    """Base dataset for trainer tests with consistent interface."""
-
-    def __init__(self, length=100, max_length=64, vocab_size=1000):
-        self.length = length
-        self.max_length = max_length
-        self.vocab_size = vocab_size
-
-    def __len__(self):
-        return self.length
-
-    def __getitem__(self, idx):
-        return {
-            "input_ids": torch.randint(0, self.vocab_size, (self.max_length,)),
-            "target_ids": torch.randint(0, self.vocab_size, (self.max_length,)),
-        }
+from tests.helpers import RandomTokenDataset
 
 
 def create_train_config(
     model_fn,
-    dataset: Dataset,
+    dataset,
     test_dir: str,
     device: str,
     strategy: str = "seq",
@@ -40,25 +22,7 @@ def create_train_config(
     random_seed: int = 42,
     **kwargs,
 ):
-    """Factory function to create common TrainConfig for tests.
-
-    Args:
-        model_fn: Model factory (callable returning nn.Module)
-        dataset: Training dataset
-        test_dir: Checkpoint directory
-        device: Device type ("cuda" or "cpu")
-        strategy: Training strategy type (default: "seq")
-        n_epoch: Number of epochs (default: 1)
-        batch_per_device: Batch size per device (default: 2)
-        grad_accum_steps: Gradient accumulation steps (default: 1)
-        max_grad_norm: Maximum gradient norm for clipping (default: 1.0)
-        ckpt_interval: Checkpoint save interval in optimizer steps (default: 5)
-        random_seed: Random seed for reproducibility (default: 42)
-        **kwargs: Additional arguments passed to TrainConfig
-
-    Returns:
-        TrainConfig instance configured for testing
-    """
+    """Factory function to create common TrainConfig for tests."""
 
     def optimizer_fn(m):
         return torch.optim.AdamW(m.parameters(), lr=0.001)
@@ -89,16 +53,11 @@ def create_train_config(
 
 @pytest.fixture
 def train_config_factory():
-    """Fixture that provides the create_train_config factory function.
-
-    This fixture can be used by tests to create consistent TrainConfig
-    instances with sensible defaults for testing.
-    """
+    """Fixture providing the ``create_train_config`` factory function."""
     return create_train_config
 
 
 @pytest.fixture
 def trainer_dataset():
     """Fixture providing a dataset for trainer tests."""
-    dataset = TrainerDataset()
-    yield dataset
+    return RandomTokenDataset()
diff --git a/tests/trainer/test_callbacks.py b/tests/trainer/test_callbacks.py
index 1ca8d66..e45eb28 100644
--- a/tests/trainer/test_callbacks.py
+++ b/tests/trainer/test_callbacks.py
@@ -1,10 +1,6 @@
-import os
-
 import torch
 
-from astrai.config.train_config import TrainConfig
 from astrai.model.components.decoder_block import DecoderBlock
-from astrai.trainer.schedule import SchedulerFactory
 from astrai.trainer.train_callback import GradientCheckpointingCallback, TrainCallback
 from astrai.trainer.trainer import Trainer
 
@@ -94,69 +90,35 @@ def test_gradient_checkpointing_backward(test_model):
         assert p.grad is None or p.grad.sum().item() == 0, f"{name} grad not zeroed"
 
 
-def test_gradient_checkpointing_trainer_integration(base_test_env, random_dataset):
+def test_gradient_checkpointing_trainer_integration(
+    base_test_env, random_dataset, train_config_factory, device
+):
     """Gradient checkpointing runs end-to-end via Trainer."""
-
-    def optimizer_fn(model):
-        return torch.optim.AdamW(model.parameters())
-
-    def scheduler_fn(optim):
-        return SchedulerFactory.create(
-            "cosine", optim, warmup_steps=10, lr_decay_steps=10, min_rate=0.05
-        )
-
-    train_config = TrainConfig(
+    train_config = train_config_factory(
         model_fn=lambda: base_test_env["model"],
-        strategy="seq",
         dataset=random_dataset,
-        optimizer_fn=optimizer_fn,
-        scheduler_fn=scheduler_fn,
-        ckpt_dir=base_test_env["test_dir"],
-        log_dir=os.path.join(base_test_env["test_dir"], "logs"),
-        n_epoch=1,
-        batch_per_device=2,
+        test_dir=base_test_env["test_dir"],
+        device=device,
         ckpt_interval=3,
-        grad_accum_steps=1,
-        max_grad_norm=1.0,
-        random_seed=42,
-        device_type=base_test_env["device"],
         gradient_checkpointing_modules=[DecoderBlock],
     )
 
     trainer = Trainer(train_config)
     trainer.train()
-    # no crash = callback correctly enabled/disabled
 
 
-def test_callback_integration(base_test_env, random_dataset):
+def test_callback_integration(
+    base_test_env, random_dataset, train_config_factory, device
+):
     """Test that all callbacks are properly integrated"""
-
-    def optimizer_fn(model):
-        return torch.optim.AdamW(model.parameters())
-
-    def scheduler_fn(optim):
-        return SchedulerFactory.create(
-            "cosine", optim, warmup_steps=10, lr_decay_steps=10, min_rate=0.05
-        )
-
-    train_config = TrainConfig(
+    train_config = train_config_factory(
         model_fn=lambda: base_test_env["model"],
-        strategy="seq",
         dataset=random_dataset,
-        optimizer_fn=optimizer_fn,
-        scheduler_fn=scheduler_fn,
-        ckpt_dir=base_test_env["test_dir"],
-        log_dir=os.path.join(base_test_env["test_dir"], "logs"),
-        n_epoch=1,
-        batch_per_device=2,
+        test_dir=base_test_env["test_dir"],
+        device=device,
         ckpt_interval=3,
-        grad_accum_steps=1,
-        max_grad_norm=1.0,
-        random_seed=42,
-        device_type=base_test_env["device"],
     )
 
-    # Create custom callbacks to track calls
     callback_calls = []
 
     class TrackingCallback(TrainCallback):
@@ -170,10 +132,8 @@ def test_callback_integration(base_test_env, random_dataset):
             callback_calls.append("on_epoch_end")
 
     trainer = Trainer(train_config, callbacks=[TrackingCallback()])
-
     trainer.train()
 
-    # Verify callbacks were called
     assert "on_train_begin" in callback_calls
     assert "on_batch_end" in callback_calls
     assert "on_epoch_end" in callback_calls
diff --git a/tests/trainer/test_early_stopping.py b/tests/trainer/test_early_stopping.py
index 2dd72ad..b3d12c5 100644
--- a/tests/trainer/test_early_stopping.py
+++ b/tests/trainer/test_early_stopping.py
@@ -1,43 +1,25 @@
 import os
 
-import numpy as np
-import torch
-
-from astrai.config.train_config import TrainConfig
-from astrai.trainer.schedule import SchedulerFactory
 from astrai.trainer.trainer import Trainer
+from tests.helpers import load_checkpoint_meta
 
 
-def test_early_stopping_simulation(base_test_env, early_stopping_dataset):
+def test_early_stopping_simulation(
+    base_test_env, early_stopping_dataset, train_config_factory, device
+):
     """Simulate early stopping behavior"""
-
-    def optimizer_fn(model):
-        return torch.optim.AdamW(model.parameters())
-
-    def scheduler_fn(optim):
-        return SchedulerFactory.create(
-            "cosine", optim, warmup_steps=10, lr_decay_steps=10, min_rate=0.05
-        )
-
-    train_config = TrainConfig(
-        strategy="seq",
-        optimizer_fn=optimizer_fn,
-        scheduler_fn=scheduler_fn,
+    train_config = train_config_factory(
         model_fn=lambda: base_test_env["model"],
         dataset=early_stopping_dataset,
-        ckpt_dir=base_test_env["test_dir"],
-        log_dir=os.path.join(base_test_env["test_dir"], "logs"),
+        test_dir=base_test_env["test_dir"],
+        device=device,
         n_epoch=2,
-        batch_per_device=2,
         ckpt_interval=1,
         grad_accum_steps=2,
-        random_seed=np.random.randint(1e4),
-        device_type=base_test_env["device"],
     )
 
     trainer = Trainer(train_config)
 
-    # Should handle early stopping gracefully
     try:
         trainer.train()
     except Exception:
@@ -50,8 +32,5 @@ def test_early_stopping_simulation(base_test_env, early_stopping_dataset):
 
     # Verify checkpoint was saved at expected step
     load_dir = os.path.join(base_test_env["test_dir"], "epoch_1_step_5")
-    import json
-
-    with open(os.path.join(load_dir, "meta.json")) as f:
-        meta = json.load(f)
+    meta = load_checkpoint_meta(load_dir)
     assert meta["consumed_samples"] == 20
diff --git a/tests/trainer/test_grpo_strategy.py b/tests/trainer/test_grpo_strategy.py
index 856d832..904800a 100644
--- a/tests/trainer/test_grpo_strategy.py
+++ b/tests/trainer/test_grpo_strategy.py
@@ -1,35 +1,9 @@
 import pytest
 import torch
 
-from astrai.config.model_config import AutoRegressiveLMConfig
 from astrai.model.transformer import AutoRegressiveLM
 from astrai.trainer.strategy import GRPOStrategy
-
-
-class _FakeExecutor:
-    """Minimal executor stub providing ``unwrap_model`` for ref model creation."""
-
-    def unwrap_model(self, model):
-        return model.state_dict()
-
-
-def _make_config(vocab_size=200, max_position_embeddings=64):
-    return AutoRegressiveLMConfig(
-        vocab_size=vocab_size,
-        hidden_size=16,
-        num_attention_heads=2,
-        num_key_value_heads=1,
-        intermediate_size=32,
-        max_position_embeddings=max_position_embeddings,
-        num_hidden_layers=2,
-        rms_norm_eps=1e-5,
-    )
-
-
-def _make_model(device):
-    config = _make_config()
-    model = AutoRegressiveLM(config).to(device=device)
-    return model, config
+from tests.helpers import FakeExecutor, make_frozen, make_model, make_rollout_config
 
 
 def _make_batch(
@@ -44,9 +18,7 @@ def _make_batch(
     responses = torch.randint(
         0, 200, (batch_size, group_size, response_len), device=device
     )
-    # All response tokens valid.
     masks = torch.ones(batch_size, group_size, response_len, device=device)
-    # Distinct rewards per group member so std > 0.
     rewards = torch.randn(batch_size, group_size, device=device)
     return {
         "prompts": prompts,
@@ -56,23 +28,12 @@ def _make_batch(
     }
 
 
-def _make_frozen_copy(model, device):
-    """Create a frozen copy of ``model`` with independent weights loaded."""
-    config = _make_config()
-    copy = AutoRegressiveLM(config).to(device=device)
-    copy.load_state_dict(model.state_dict())
-    copy.requires_grad_(False)
-    copy.eval()
-    return copy
-
-
 @pytest.fixture
-def grpo_strategy():
+def grpo_strategy(device):
     """Build a GRPOStrategy with a small real model and fake executor."""
-    device = "cuda" if torch.cuda.is_available() else "cpu"
-    model, config = _make_model(device)
-    old_model = _make_frozen_copy(model, device)
-    ref_model = _make_frozen_copy(model, device)
+    model, config = make_model(device)
+    old_model = make_frozen(model, device)
+    ref_model = make_frozen(model, device)
 
     strategy = GRPOStrategy(
         model=model,
@@ -83,7 +44,7 @@ def grpo_strategy():
         kl_coef=0.01,
         group_size=4,
         model_fn=lambda c=config: AutoRegressiveLM(c).to(device=device),
-        executor=_FakeExecutor(),
+        executor=FakeExecutor(),
     )
     return strategy, device
 
@@ -103,7 +64,6 @@ def test_grpo_loss_backward(grpo_strategy):
     batch = _make_batch(device=device)
     loss = strategy.compute_loss(batch)
     loss.backward()
-    # At least some parameter should receive a gradient.
     has_grad = any(
         p.grad is not None and p.grad.abs().sum().item() > 0
         for p in strategy.model.parameters()
@@ -136,32 +96,27 @@ def test_grpo_prompt_tokens_masked(grpo_strategy):
     the policy loss should be zero (no valid tokens contribute)."""
     strategy, device = grpo_strategy
     batch = _make_batch(device=device)
-    # Zero out all response masks → no response token contributes.
     batch["masks"] = torch.zeros_like(batch["masks"])
     loss = strategy.compute_loss(batch)
-    # With no valid tokens, policy_loss term is 0 and KL term is 0.
     assert loss.item() == pytest.approx(0.0, abs=1e-6)
 
 
 def test_grpo_identical_rewards_zero_advantage(grpo_strategy):
-    """When all group rewards are identical, advantage is 0 → policy_loss is 0.
+    """When all group rewards are identical, advantage is 0 -> policy_loss is 0.
     Only the KL term remains (which is 0 when policy == ref at init)."""
     strategy, device = grpo_strategy
     batch = _make_batch(device=device)
     batch["rewards"] = torch.ones(batch["rewards"].shape, device=device)
     loss = strategy.compute_loss(batch)
-    # At init policy == old == ref, so ratio == 1, KL == 0; advantage == 0.
     assert loss.item() == pytest.approx(0.0, abs=1e-5)
 
 
 def test_grpo_sync_old_model(grpo_strategy):
     """sync_old_model copies current policy weights into old_model."""
     strategy, device = grpo_strategy
-    # Perturb policy model so it differs from old.
     with torch.no_grad():
         for p in strategy.model.parameters():
             p.add_(0.05)
-    # old_model should still hold original weights (differ from policy).
     policy_sd = strategy.model.state_dict()
     old_sd = strategy.old_model.state_dict()
     differs_before = any(
@@ -195,14 +150,12 @@ def test_grpo_clipping_effect(grpo_strategy):
     """After diverging policy from ref, ratio should be clipped to [1-eps, 1+eps]
     on the surrogate. Verify loss is finite and non-zero for distinct rewards."""
     strategy, device = grpo_strategy
-    # Diverge policy from ref.
     with torch.no_grad():
         for p in strategy.model.parameters():
             p.add_(0.3)
     batch = _make_batch(device=device)
     loss = strategy.compute_loss(batch)
     assert torch.isfinite(loss).item()
-    # With distinct rewards and diverged policy, loss should be non-trivial.
     assert loss.abs().item() > 1e-4
 
 
diff --git a/tests/trainer/test_online_e2e.py b/tests/trainer/test_online_e2e.py
index 516e6a7..7570825 100644
--- a/tests/trainer/test_online_e2e.py
+++ b/tests/trainer/test_online_e2e.py
@@ -12,19 +12,7 @@ from astrai.model.transformer import AutoRegressiveLM
 from astrai.trainer.rollout import BaseRewardModel
 from astrai.trainer.schedule import SchedulerFactory
 from astrai.trainer.trainer import Trainer
-
-_CHAT_TEMPLATE = (
-    "{% for message in messages %}"
-    "{% if message['role'] == 'system' %}"
-    "SYSTEM: {{ message['content'] }}\n"
-    "{% elif message['role'] == 'user' %}"
-    "USER: {{ message['content'] }}\n"
-    "{% elif message['role'] == 'assistant' %}"
-    "ASSISTANT: {{ message['content'] }}\n"
-    "{% endif %}"
-    "{% endfor %}"
-    "{% if add_generation_prompt %}ASSISTANT: {% endif %}"
-)
+from tests.helpers import CHAT_TEMPLATE
 
 
 class InstructionDataset(Dataset):
@@ -97,7 +85,7 @@ def test_online_dpo_end_to_end(base_test_env):
 
     # Equip tokenizer with a chat template so RolloutGenerator can
     # render instruction/input via apply_chat_template.
-    tokenizer.set_chat_template(_CHAT_TEMPLATE)
+    tokenizer.set_chat_template(CHAT_TEMPLATE)
     tokenizer.save_pretrained(test_dir)
 
     model_fn = partial(_model_fn, model_config)
diff --git a/tests/trainer/test_online_strategy.py b/tests/trainer/test_online_strategy.py
index 34c88d1..91544ba 100644
--- a/tests/trainer/test_online_strategy.py
+++ b/tests/trainer/test_online_strategy.py
@@ -9,7 +9,6 @@ the per-strategy ``prepare_from_rollout`` mappings for both
 import pytest
 import torch
 
-from astrai.config.model_config import AutoRegressiveLMConfig
 from astrai.model.transformer import AutoRegressiveLM
 from astrai.trainer.rollout import RolloutResult
 from astrai.trainer.strategy import (
@@ -17,47 +16,7 @@ from astrai.trainer.strategy import (
     GRPOStrategy,
     StrategyFactory,
 )
-
-
-class _FakeExecutor:
-    """Executor stub tracking ``sync_gradients`` and providing unwrap_model."""
-
-    def __init__(self, sync_gradients=True):
-        self._sync_gradients = sync_gradients
-
-    @property
-    def sync_gradients(self):
-        return self._sync_gradients
-
-    def unwrap_model(self, model):
-        return model.state_dict()
-
-
-def _make_config(vocab_size=200, max_position_embeddings=64):
-    return AutoRegressiveLMConfig(
-        vocab_size=vocab_size,
-        hidden_size=16,
-        num_attention_heads=2,
-        num_key_value_heads=1,
-        intermediate_size=32,
-        max_position_embeddings=max_position_embeddings,
-        num_hidden_layers=2,
-        rms_norm_eps=1e-5,
-    )
-
-
-def _make_model(device):
-    cfg = _make_config()
-    return AutoRegressiveLM(cfg).to(device=device), cfg
-
-
-def _make_frozen(model, device):
-    cfg = _make_config()
-    copy = AutoRegressiveLM(cfg).to(device=device)
-    copy.load_state_dict(model.state_dict())
-    copy.requires_grad_(False)
-    copy.eval()
-    return copy
+from tests.helpers import FakeExecutor, make_frozen, make_model, make_rollout_config
 
 
 def _make_rollout_result(B=2, G=4, P=6, R=8, device="cpu"):
@@ -75,7 +34,7 @@ class _RecordingRunner:
     """Fake RolloutRunner returning a fixed result with freshness tracking.
 
     Freshness is ``True`` on the first call after construction or after
-    :meth:`swap_result`; ``False`` on subsequent cached calls — mirroring
+    :meth:`swap_result`; ``False`` on subsequent cached calls -- mirroring
     the real ``RolloutRunner`` contract without invoking generation.
     """
 
@@ -99,15 +58,10 @@ class _RecordingRunner:
         self._fresh = True
 
 
-@pytest.fixture
-def device():
-    return "cuda" if torch.cuda.is_available() else "cpu"
-
-
 def _make_grpo(device, executor=None):
-    model, _ = _make_model(device)
-    old_model = _make_frozen(model, device)
-    ref_model = _make_frozen(model, device)
+    model, _ = make_model(device)
+    old_model = make_frozen(model, device)
+    ref_model = make_frozen(model, device)
     return GRPOStrategy(
         model=model,
         device=device,
@@ -116,22 +70,22 @@ def _make_grpo(device, executor=None):
         clip_eps=0.2,
         kl_coef=0.01,
         group_size=4,
-        model_fn=lambda c=_make_config(): AutoRegressiveLM(c).to(device=device),
-        executor=executor or _FakeExecutor(),
+        model_fn=lambda c=make_rollout_config(): AutoRegressiveLM(c).to(device=device),
+        executor=executor or FakeExecutor(),
     )
 
 
 def _make_dpo(device, executor=None):
-    model, _ = _make_model(device)
-    ref_model = _make_frozen(model, device)
+    model, _ = make_model(device)
+    ref_model = make_frozen(model, device)
     return DPOStrategy(
         model=model,
         device=device,
         ref_model=ref_model,
         beta=0.1,
         reduction="sum",
-        model_fn=lambda c=_make_config(): AutoRegressiveLM(c).to(device=device),
-        executor=executor or _FakeExecutor(),
+        model_fn=lambda c=make_rollout_config(): AutoRegressiveLM(c).to(device=device),
+        executor=executor or FakeExecutor(),
     )
 
 
@@ -295,7 +249,7 @@ def test_dpo_no_sync_hook_when_new_rollout_result(device):
 
 
 def test_step_not_called_when_sync_gradients_false(device):
-    executor = _FakeExecutor(sync_gradients=False)
+    executor = FakeExecutor(sync_gradients=False)
     strat = _make_grpo(device, executor=executor)
     runner = _RecordingRunner(_make_rollout_result(device=device))
     strat.set_rollout_runner(runner)
@@ -304,7 +258,7 @@ def test_step_not_called_when_sync_gradients_false(device):
 
 
 def test_step_called_when_sync_gradients_true(device):
-    executor = _FakeExecutor(sync_gradients=True)
+    executor = FakeExecutor(sync_gradients=True)
     strat = _make_grpo(device, executor=executor)
     runner = _RecordingRunner(_make_rollout_result(device=device))
     strat.set_rollout_runner(runner)
diff --git a/tests/trainer/test_rollout.py b/tests/trainer/test_rollout.py
index 34cc8bd..94d5630 100644
--- a/tests/trainer/test_rollout.py
+++ b/tests/trainer/test_rollout.py
@@ -3,9 +3,7 @@
 import pytest
 import torch
 
-from astrai.config.model_config import AutoRegressiveLMConfig
 from astrai.inference.core.scheduler import InferenceScheduler
-from astrai.model.transformer import AutoRegressiveLM
 from astrai.trainer.rollout import (
     BaseRewardModel,
     RawRollout,
@@ -13,50 +11,7 @@ from astrai.trainer.rollout import (
     RolloutResult,
     RolloutRunner,
 )
-
-_CHAT_TEMPLATE = (
-    "{% for message in messages %}"
-    "{% if message['role'] == 'system' %}SYSTEM: {{ message['content'] }}\n{% endif %}"
-    "{% if message['role'] == 'user' %}USER: {{ message['content'] }}\n{% endif %}"
-    "{% if message['role'] == 'assistant' %}ASSISTANT: {{ message['content'] }}\n{% endif %}"
-    "{% endfor %}"
-    "{% if add_generation_prompt %}ASSISTANT: {% endif %}"
-)
-
-
-class FakeTokenizer:
-    """Minimal stub tokenizer with a chat template for rollout tests."""
-
-    stop_ids = [2]
-
-    def __init__(self):
-        from astrai.tokenize.chat_template import ChatTemplate
-
-        self._chat_template = ChatTemplate.from_string(_CHAT_TEMPLATE)
-
-    def encode(self, texts, **_):
-        if isinstance(texts, str):
-            texts = [texts]
-        return [[b for b in t.encode("utf-8")] for t in texts]
-
-    def decode(self, ids, skip_special_tokens=True):
-        if isinstance(ids, list):
-            return bytes(b for b in ids if b > 2).decode("utf-8", errors="ignore")
-        return str(ids)
-
-    def apply_chat_template(
-        self, messages, tokenize=True, add_generation_prompt=True, **_
-    ):
-        rendered = self._chat_template.render(
-            messages=messages, add_generation_prompt=add_generation_prompt
-        )
-        if tokenize:
-            return (
-                self.encode(rendered)[0]
-                if isinstance(rendered, str)
-                else [self.encode(t)[0] for t in rendered]
-            )
-        return rendered
+from tests.helpers import FakeTokenizer, make_model
 
 
 class ConstantRewardModel(BaseRewardModel):
@@ -83,26 +38,6 @@ class NonFiniteRewardModel(BaseRewardModel):
         return torch.full((B, G), float("nan"))
 
 
-def _make_config(vocab_size=200, max_position_embeddings=128):
-    return AutoRegressiveLMConfig(
-        vocab_size=vocab_size,
-        hidden_size=16,
-        num_attention_heads=2,
-        num_key_value_heads=1,
-        intermediate_size=32,
-        max_position_embeddings=max_position_embeddings,
-        num_hidden_layers=2,
-        rms_norm_eps=1e-5,
-    )
-
-
-def _make_model(device):
-    cfg = _make_config()
-    m = AutoRegressiveLM(cfg).to(device=device)
-    m.eval()
-    return m, cfg
-
-
 def _make_scheduler(model, tokenizer, max_batch_size=8, max_len=128):
     return InferenceScheduler(
         model=model,
@@ -160,14 +95,9 @@ def test_constant_reward_model_shape():
     assert torch.all(out == 0.5)
 
 
-@pytest.fixture
-def device():
-    return "cuda" if torch.cuda.is_available() else "cpu"
-
-
 def _make_generator(device, **kw):
-    model, _ = _make_model(device)
-    tokenizer = FakeTokenizer()
+    model, _ = make_model(device, max_position_embeddings=128)
+    tokenizer = FakeTokenizer(with_chat_template=True)
     scheduler = _make_scheduler(
         model,
         tokenizer,
@@ -229,7 +159,7 @@ def test_rollout_generator_mask_matches_responses(device):
 
 
 def test_rollout_generator_logprobs_are_nonpositive(device):
-    """Behaviour-policy logprobs of sampled tokens should be ≤ 0."""
+    """Behaviour-policy logprobs of sampled tokens should be <= 0."""
     gen, _ = _make_generator(device, group_size=2, max_tokens=4)
     batch = _make_instruction_batch(n=1)
     r = gen.generate(batch)
@@ -241,7 +171,7 @@ def test_rollout_generator_logprobs_are_nonpositive(device):
 
 
 def test_rollout_generator_instruction_role_mapping(device):
-    """instruction → system, input → user, output → assistant."""
+    """instruction -> system, input -> user, output -> assistant."""
     gen, _ = _make_generator(device, group_size=1, max_tokens=4)
     batch = {
         "instruction": ["Be helpful"],
diff --git a/tests/trainer/test_signal_handler.py b/tests/trainer/test_signal_handler.py
index d219438..9d74f69 100644
--- a/tests/trainer/test_signal_handler.py
+++ b/tests/trainer/test_signal_handler.py
@@ -1,4 +1,3 @@
-import json
 import multiprocessing as mp
 import os
 import signal
@@ -10,15 +9,15 @@ import torch.optim as optim
 from torch.utils.data import Dataset
 
 from astrai.config import TrainConfig
-from astrai.config.model_config import AutoRegressiveLMConfig
 from astrai.model.transformer import AutoRegressiveLM
 from astrai.parallel.signal_handler import register_signal_handlers
 from astrai.trainer import Trainer
 from astrai.trainer.schedule import SchedulerFactory
 from astrai.trainer.train_context import TrainContext
+from tests.helpers import load_checkpoint_meta, make_tiny_config
 
 
-class _PicklableDataset(Dataset):
+class PicklableDataset(Dataset):
     def __init__(self, length=200, max_length=64, vocab_size=1000):
         self.length = length
         self.max_length = max_length
@@ -35,16 +34,7 @@ class _PicklableDataset(Dataset):
 
 
 def _build_model():
-    config = AutoRegressiveLMConfig(
-        vocab_size=1000,
-        hidden_size=8,
-        num_attention_heads=2,
-        num_key_value_heads=1,
-        intermediate_size=16,
-        max_position_embeddings=64,
-        num_hidden_layers=2,
-        rms_norm_eps=1e-5,
-    )
+    config = make_tiny_config()
     device = "cuda" if torch.cuda.is_available() else "cpu"
     return AutoRegressiveLM(config).to(device=device)
 
@@ -61,7 +51,7 @@ class _ReadyCallback:
 
 
 def _inner_run(batch_per_device, ckpt_interval, ckpt_dir, log_dir, ready_file):
-    dataset = _PicklableDataset()
+    dataset = PicklableDataset()
 
     def model_fn():
         return _build_model()
@@ -147,17 +137,7 @@ def test_sigterm_triggers_checkpoint_save(base_test_env):
     exitcode = _spawn_train_and_signal(base_test_env["test_dir"], signal.SIGTERM)
     assert exitcode == 0, f"Training process exited with code {exitcode} (expected 0)"
 
-    ckpt_dir = base_test_env["test_dir"]
-    meta_files = []
-    for root, dirs, files in os.walk(ckpt_dir):
-        for f in files:
-            if f == "meta.json":
-                meta_files.append(os.path.join(root, f))
-
-    assert len(meta_files) > 0, f"No checkpoint meta.json found in {ckpt_dir}"
-
-    with open(meta_files[-1]) as f:
-        meta = json.load(f)
+    meta = load_checkpoint_meta(base_test_env["test_dir"])
     assert "consumed_samples" in meta
     assert meta["consumed_samples"] >= 0
 
@@ -167,11 +147,6 @@ def test_sigint_triggers_checkpoint_save(base_test_env):
     exitcode = _spawn_train_and_signal(base_test_env["test_dir"], signal.SIGINT)
     assert exitcode == 0, f"Training process exited with code {exitcode} (expected 0)"
 
-    ckpt_dir = base_test_env["test_dir"]
-    meta_files = []
-    for root, dirs, files in os.walk(ckpt_dir):
-        for f in files:
-            if f == "meta.json":
-                meta_files.append(os.path.join(root, f))
-
-    assert len(meta_files) > 0, f"No checkpoint meta.json found in {ckpt_dir}"
+    meta = load_checkpoint_meta(base_test_env["test_dir"])
+    assert "consumed_samples" in meta
+    assert meta["consumed_samples"] >= 0