diff --git a/tests/CacheTest.cpp b/tests/CacheTest.cpp
new file mode 100644
index 0000000000..4649797e6a
--- /dev/null
+++ b/tests/CacheTest.cpp
@@ -0,0 +1,229 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#include <gtest/gtest.h>
+
+#include <yoga/Yoga.h>
+#include <yoga/algorithm/Cache.h>
+#include <yoga/algorithm/SizingMode.h>
+#include <yoga/config/Config.h>
+
+namespace facebook::yoga {
+
+class CacheTest : public ::testing::Test {
+ protected:
+  void SetUp() override {
+    config_ = static_cast<yoga::Config*>(YGConfigNew());
+  }
+
+  void TearDown() override {
+    YGConfigFree(config_);
+  }
+
+  yoga::Config* config_ = nullptr;
+};
+
+TEST_F(CacheTest, negativeCachedMeasurementDisablesCache) {
+  // Cached values with defined-but-negative extents are treated as invalid;
+  // both axes must independently invalidate the cache.
+  const bool negativeWidth = canUseCachedMeasurement(
+      SizingMode::StretchFit,
+      100.0f,
+      SizingMode::StretchFit,
+      50.0f,
+      SizingMode::StretchFit,
+      100.0f,
+      SizingMode::StretchFit,
+      50.0f,
+      /*lastComputedWidth=*/-1.0f,
+      /*lastComputedHeight=*/50.0f,
+      0.0f,
+      0.0f,
+      config_);
+  EXPECT_FALSE(negativeWidth);
+
+  const bool negativeHeight = canUseCachedMeasurement(
+      SizingMode::StretchFit,
+      100.0f,
+      SizingMode::StretchFit,
+      50.0f,
+      SizingMode::StretchFit,
+      100.0f,
+      SizingMode::StretchFit,
+      50.0f,
+      /*lastComputedWidth=*/100.0f,
+      /*lastComputedHeight=*/-0.5f,
+      0.0f,
+      0.0f,
+      config_);
+  EXPECT_FALSE(negativeHeight);
+}
+
+TEST_F(CacheTest, identicalSpecsAllowCacheReuse) {
+  // Primary cache-hit path: identical mode + available size on both axes
+  // means the previously computed measurement can be reused verbatim.
+  const bool canUse = canUseCachedMeasurement(
+      SizingMode::StretchFit,
+      100.0f,
+      SizingMode::FitContent,
+      50.0f,
+      SizingMode::StretchFit,
+      100.0f,
+      SizingMode::FitContent,
+      50.0f,
+      /*lastComputedWidth=*/95.0f,
+      /*lastComputedHeight=*/45.0f,
+      0.0f,
+      0.0f,
+      config_);
+
+  EXPECT_TRUE(canUse);
+}
+
+TEST_F(CacheTest, incompatibleSpecsDisableCache) {
+  // Previous run used MaxContent with a computed size of 95; the new run
+  // stretches to 200. StretchFit only reuses a cached size when the new
+  // inner extent equals the last computed size, which does not hold here,
+  // so no compatibility branch applies.
+  const bool canUse = canUseCachedMeasurement(
+      SizingMode::StretchFit,
+      200.0f,
+      SizingMode::StretchFit,
+      200.0f,
+      SizingMode::MaxContent,
+      YGUndefined,
+      SizingMode::MaxContent,
+      YGUndefined,
+      /*lastComputedWidth=*/95.0f,
+      /*lastComputedHeight=*/95.0f,
+      0.0f,
+      0.0f,
+      config_);
+
+  EXPECT_FALSE(canUse);
+}
+
+TEST_F(
+    CacheTest,
+    stretchFitMatchingComputedSizeReusesCacheAccountingForMargin) {
+  // Under StretchFit, the requested content size is (availableWidth -
+  // marginRow) = 90, which matches the last computed width of 90. This
+  // hits the sizeIsExactAndMatchesOldMeasuredSize branch and also verifies
+  // that marginRow is subtracted before the comparison (a bare 100 would
+  // not match 90).
+  const bool canUse = canUseCachedMeasurement(
+      SizingMode::StretchFit,
+      /*availableWidth=*/100.0f,
+      SizingMode::StretchFit,
+      /*availableHeight=*/60.0f,
+      SizingMode::FitContent,
+      /*lastAvailableWidth=*/90.0f,
+      SizingMode::StretchFit,
+      /*lastAvailableHeight=*/60.0f,
+      /*lastComputedWidth=*/90.0f,
+      /*lastComputedHeight=*/60.0f,
+      /*marginRow=*/10.0f,
+      /*marginColumn=*/0.0f,
+      config_);
+
+  EXPECT_TRUE(canUse);
+}
+
+TEST_F(CacheTest, maxContentResultStillFitsFitContentRequest) {
+  // Cached MaxContent width of 80 fits inside a FitContent request with 120
+  // available space, so the previous result remains valid (the max-content
+  // size cannot overflow the looser constraint).
+  const bool canUse = canUseCachedMeasurement(
+      SizingMode::FitContent,
+      /*availableWidth=*/120.0f,
+      SizingMode::StretchFit,
+      /*availableHeight=*/50.0f,
+      SizingMode::MaxContent,
+      /*lastAvailableWidth=*/YGUndefined,
+      SizingMode::StretchFit,
+      /*lastAvailableHeight=*/50.0f,
+      /*lastComputedWidth=*/80.0f,
+      /*lastComputedHeight=*/50.0f,
+      0.0f,
+      0.0f,
+      config_);
+
+  EXPECT_TRUE(canUse);
+}
+
+TEST_F(CacheTest, tighterFitContentReusesCacheWhenPreviousResultStillFits) {
+  // Both runs use FitContent. The new available width (100) is stricter than
+  // the previous one (150), but the previously computed width (80) still
+  // fits inside the new constraint, so the cached measurement is reusable.
+  const bool canUse = canUseCachedMeasurement(
+      SizingMode::FitContent,
+      /*availableWidth=*/100.0f,
+      SizingMode::StretchFit,
+      /*availableHeight=*/50.0f,
+      SizingMode::FitContent,
+      /*lastAvailableWidth=*/150.0f,
+      SizingMode::StretchFit,
+      /*lastAvailableHeight=*/50.0f,
+      /*lastComputedWidth=*/80.0f,
+      /*lastComputedHeight=*/50.0f,
+      0.0f,
+      0.0f,
+      config_);
+
+  EXPECT_TRUE(canUse);
+}
+
+TEST_F(
+    CacheTest,
+    tighterFitContentInvalidatesCacheWhenPreviousResultOverflows) {
+  // Same shape as the previous test but the cached width (120) is larger
+  // than the tightened constraint (100). Reusing the measurement would
+  // silently overflow the container, so the cache must be discarded.
+  const bool canUse = canUseCachedMeasurement(
+      SizingMode::FitContent,
+      /*availableWidth=*/100.0f,
+      SizingMode::StretchFit,
+      /*availableHeight=*/50.0f,
+      SizingMode::FitContent,
+      /*lastAvailableWidth=*/150.0f,
+      SizingMode::StretchFit,
+      /*lastAvailableHeight=*/50.0f,
+      /*lastComputedWidth=*/120.0f,
+      /*lastComputedHeight=*/50.0f,
+      0.0f,
+      0.0f,
+      config_);
+
+  EXPECT_FALSE(canUse);
+}
+
+TEST_F(CacheTest, pixelGridRoundingMakesSubPixelSpecsEquivalent) {
+  // At a point scale factor of 2, both 10.25 and 10.5 snap to 10.5 on the
+  // physical pixel grid. Specs that differ by less than one device pixel
+  // must be treated as identical so we can reuse the cache; without grid
+  // rounding, inexactEquals(10.25, 10.5) is false and the cache would miss.
+  config_->setPointScaleFactor(2.0f);
+
+  const bool canUse = canUseCachedMeasurement(
+      SizingMode::StretchFit,
+      /*availableWidth=*/10.25f,
+      SizingMode::StretchFit,
+      /*availableHeight=*/20.0f,
+      SizingMode::StretchFit,
+      /*lastAvailableWidth=*/10.5f,
+      SizingMode::StretchFit,
+      /*lastAvailableHeight=*/20.0f,
+      /*lastComputedWidth=*/10.5f,
+      /*lastComputedHeight=*/20.0f,
+      0.0f,
+      0.0f,
+      config_);
+
+  EXPECT_TRUE(canUse);
+}
+
+} // namespace facebook::yoga