test: add unit tests for warmup.py helpers (#274)

* test: add unit tests for warmup.py helpers

* fix: ruff lint fixes (import order + trailing newline)

* fix: add trailing newline

* style: ruff --fix

tests/test_warmup.py

@@ -0,0 +1,96 @@
+import pytest
+
+from soup_cli.utils.warmup import MAX_WARMUP, MIN_WARMUP, compute_warmup_steps
+
+# --- Happy path ---
+
+def test_typical_inputs_returns_clamped_value():
+    result = compute_warmup_steps(
+        num_examples=1000, batch_size=8, grad_accum=1, epochs=3
+    )
+    assert MIN_WARMUP <= result <= MAX_WARMUP
+
+
+def test_default_ratio_used_when_not_specified():
+    result = compute_warmup_steps(1000, 8, 1, 3)
+    assert isinstance(result, int)
+
+
+# --- ratio=0 special case ---
+
+def test_zero_ratio_returns_zero():
+    result = compute_warmup_steps(1000, 8, 1, 3, ratio=0.0)
+    assert result == 0
+
+
+# --- Clamping ---
+
+def test_clamps_to_min_warmup_for_tiny_dataset():
+    result = compute_warmup_steps(
+        num_examples=10, batch_size=8, grad_accum=1, epochs=1, ratio=0.03
+    )
+    assert result == MIN_WARMUP
+
+
+def test_clamps_to_max_warmup_for_huge_dataset():
+    result = compute_warmup_steps(
+        num_examples=1_000_000, batch_size=1, grad_accum=1, epochs=10, ratio=0.5
+    )
+    assert result == MAX_WARMUP
+
+
+# --- Bounds ---
+
+def test_max_ratio_accepted():
+    result = compute_warmup_steps(1000, 8, 1, 3, ratio=0.5)
+    assert MIN_WARMUP <= result <= MAX_WARMUP
+
+
+def test_grad_accum_reduces_steps():
+    result_no_accum = compute_warmup_steps(1000, 8, 1, 3)
+    result_with_accum = compute_warmup_steps(1000, 8, 4, 3)
+    assert result_with_accum <= result_no_accum
+
+
+# --- Edge cases ---
+
+def test_single_example():
+    result = compute_warmup_steps(1, 1, 1, 1)
+    assert result == MIN_WARMUP
+
+
+def test_single_epoch():
+    result = compute_warmup_steps(500, 8, 1, 1)
+    assert MIN_WARMUP <= result <= MAX_WARMUP
+
+
+# --- Validation errors ---
+
+def test_raises_for_zero_examples():
+    with pytest.raises(ValueError, match="num_examples"):
+        compute_warmup_steps(0, 8, 1, 3)
+
+
+def test_raises_for_zero_batch_size():
+    with pytest.raises(ValueError, match="batch_size"):
+        compute_warmup_steps(1000, 0, 1, 3)
+
+
+def test_raises_for_zero_grad_accum():
+    with pytest.raises(ValueError, match="grad_accum"):
+        compute_warmup_steps(1000, 8, 0, 3)
+
+
+def test_raises_for_zero_epochs():
+    with pytest.raises(ValueError, match="epochs"):
+        compute_warmup_steps(1000, 8, 1, 0)
+
+
+def test_raises_for_ratio_above_max():
+    with pytest.raises(ValueError, match="ratio"):
+        compute_warmup_steps(1000, 8, 1, 3, ratio=0.6)
+
+
+def test_raises_for_negative_ratio():
+    with pytest.raises(ValueError, match="ratio"):
+        compute_warmup_steps(1000, 8, 1, 3, ratio=-0.1)