Fidelity report

The mock engine is a reimplementation of React Native, so it could in principle drift from real RN. vitest-native guards against that with a behavioral cross-check: a corpus of probes runs the same assertions under the mock engine and under real React Native, and any divergence fails CI. This page is generated from the corpus itself, so the numbers below are exactly what ships.

Summary

• 85 / 85 probes match between the mock engine and real React Native (this page was generated against React Native 0.86.0).
• CI runs the same corpus across React Native 0.81–0.86 on every commit.
• Per-version results straight from the CI matrix: Fidelity Matrix.
• Reproduce it yourself: bun run crosscheck.

What this number covers

A matching probe count says how many comparisons pass, not how much of the mock they reach. The corpus reaches 12 of 27 mocked APIs and 16 of 24 mocked components. The rest are not compared against real React Native at all — they are not known to differ, they are simply unmeasured.

Not reached by any probe:

• APIs: AccessibilityInfo, ActionSheetIOS, Alert, BackHandler, Clipboard, Keyboard, Linking, LogBox, PanResponder, PermissionsAndroid, Share, ToastAndroid, Vibration, useColorScheme, useWindowDimensions
• Components: DrawerLayoutAndroid, ImageBackground, InputAccessoryView, RefreshControl, SafeAreaView, StatusBar, TouchableNativeFeedback, VirtualizedList

The native engine needs no cross-check — it is real React Native.

Probes

Each probe renders or exercises a real behavior (queries, presses, text input, lists, scrolling, modals, and core API values) and compares the observable result across both engines.

Probe	Result
a11y-role	✅ match
a11y-state-disabled	✅ match
accessibility-label-read	✅ match
accessibility-value	✅ match
activityindicator-renders	✅ match
animated-image-renders	✅ match
animated-interpolation-live-style	✅ match
animated-scrollview-renders	✅ match
animated-setvalue-updates-rendered-style	✅ match
animated-surface	✅ match
animated-text-renders	✅ match
animated-transform-live-style	✅ match
animated-value-initial-style	✅ match
animated-view-renders	✅ match
button-renders-title	✅ match
button-userpress	✅ match
composite-text-match	✅ match
controlled-textinput-rerender	✅ match
device-event-emitter	✅ match
dimensions-window	✅ match
easing-curves	✅ match
easing-parameterised	✅ match
flatlist-renders-items	✅ match
get-all-by-role-count	✅ match
get-by-text-miss-throws	✅ match
hunt-fireevent-press	✅ match
hunt-pressable-children-fn	✅ match
hunt-pressable-disabled-a11ystate	✅ match
hunt-pressable-press-in-out	✅ match
hunt-pressable-style-fn	✅ match
hunt-processcolor-edge	✅ match
hunt-stylesheet-flatten-direct-falsy	✅ match
hunt-textinput-maxlength	✅ match
i18nmanager-isrtl	✅ match
image-render	✅ match
interaction-manager	✅ match
keyboardavoidingview-children	✅ match
layout-animation-presets	✅ match
matcher-checked-switch	✅ match
matcher-contains-element	✅ match
matcher-disabled-enabled	✅ match
matcher-display-value	✅ match
matcher-have-prop	✅ match
matcher-on-the-screen	✅ match
matcher-style	✅ match
matcher-text-content	✅ match
modal-visible-children	✅ match
nested-text	✅ match
not-on-screen-after-unmount	✅ match
pixelratio	✅ match
pixelratio-rounding	✅ match
placeholder-query	✅ match
platform-os	✅ match
platform-select	✅ match
platform-select-partial	✅ match
platform-version-type	✅ match
pressable-disabled-suppresses-press	✅ match
pressable-fires-onpress	✅ match
processcolor	✅ match
query-all-by-text	✅ match
query-by-hint-text	✅ match
query-by-label-text	✅ match
query-by-role	✅ match
query-by-role-name	✅ match
query-by-testid-miss	✅ match
query-by-text-regex	✅ match
scrollview-fireevent-scroll	✅ match
sectionlist-render	✅ match
stylesheet-create-identity	✅ match
stylesheet-flatten	✅ match
stylesheet-flatten-falsy	✅ match
stylesheet-helpers	✅ match
switch-render	✅ match
testid-query	✅ match
text-numberoflines-prop	✅ match
text-renders	✅ match
textinput-displayvalue	✅ match
textinput-focus-blur	✅ match
textinput-onchangetext	✅ match
textinput-usertype	✅ match
touchable-highlight-onpress	✅ match
touchable-opacity-onpress	✅ match
touchable-without-feedback-onpress	✅ match
view-onlayout	✅ match
within-scoping	✅ match

Not gated by the cross-check

Some behaviors are deliberately left out of the gated corpus above because they vary by React Native version, test environment, or device — a single fixed value can't be correct for all of them, so pinning one would make the cross-check lie. They are documented here rather than hidden.

Area	Behavior	Why it isn't gated
Default device metrics (Dimensions / PixelRatio)	The default window/screen size, pixel ratio and font scale are a fixed test-host default. Both engines report the same default — the cross-check gates that — but it is not any specific physical device.	Device metrics aren't behavior, and the default won't match a real device. Tests that depend on exact metrics should set them explicitly (e.g. Dimensions.set) rather than rely on the default.
Text onPress accessibilityRole	A <Text> with an onPress handler is auto-assigned accessibilityRole "link" by some React Native versions and not others.	Version-variant across the supported RN range — a single mock value can't match every minor, so it isn't pinned by a probe.
Appearance color scheme	Appearance.getColorScheme() reflects the host environment rather than a fixed value.	Environment-dependent (CI vs local, OS settings), so it isn't a stable cross-engine invariant to gate.
AppState.currentState	The mock engine reports "active" (a foregrounded app). Real React Native running under Node reports undefined, because it reads the value from a native module that only exists on a device — as it also does under Jest with React Native's own preset.	Not a cross-engine invariant: the value exists only because a device exists, the same case as the default device metrics above. The mock's value is pinned by its own suite so it cannot drift unnoticed; tests that branch on foreground state should set it explicitly rather than rely on either default.
Animated.getValue()	The mock engine adds a getValue() convenience reader to animated nodes. Real React Native exposes only the internal __getValue(), so the same call throws under engine:native. Separately, this mock applies timing/spring/decay synchronously rather than routing them through AnimatedValue.animate(), which real React Native does — so a suite spying on animate() observes nothing under the mock engine and a call under the native one.	Kept for suites already using it, and it now warns once per process pointing at __getValue(), which works under both engines. Removing it is a breaking change and belongs in a major. Every other difference in the Animated surface has been closed: the mock now implements Animated.Node, Animated.Event, Animated.Interpolation, attachNativeEvent, Value.track/stopTracking/animate, hasListeners and toJSON, and stopAnimation/resetAnimation moved off the shared base class to Value and Color, where React Native has them.
Host component names and snapshots	The mock engine renders host elements under their JavaScript component name — View, Text, TextInput — while real React Native uses the native view name: RCTView, RCTText. Real React Native also attaches props the mock leaves unset (a Text host carries allowFontScaling, ellipsizeMode and a style array beginning with { overflow: "hidden" }).	React Native Testing Library detects host component names at runtime, so queries, matchers and fireEvent behave identically either way and the corpus above verifies that. SNAPSHOTS DO NOT TRANSFER: the serializer prints the host name and the props verbatim, so a snapshot recorded under one engine fails under the other. Record snapshots under the engine the suite runs on, and re-record when switching.
InteractionManager.runAfterInteractions timing	The mock runs the task synchronously, during the runAfterInteractions() call. Real React Native defers it, so it has not run when the call returns and has run a tick later. Both run it exactly once.	A test asserting on the result immediately after the call passes under the mock engine and fails under the native one. Awaiting a tick, or asserting through findBy* queries, works under both. Making the mock defer would match React Native and Jest but breaks suites written against the synchronous behaviour, so it is disclosed rather than changed.