migrate pure-logic tests to vitest (phase 1)

vitest/react-native-stub.ts

@@ -0,0 +1,27 @@
+/*
+ * Stub for `react-native` used in unit tests. react-native's real entry is
+ * Flow-typed and boots a native runtime, neither of which works (or is needed)
+ * under Vitest's node environment. This is aliased in place of `react-native`
+ * via resolve.alias in vitest.config.ts.
+ *
+ * Only the surface our test-reachable modules actually touch is implemented:
+ * - Image.getSize (src/lib/media/manip.ts)
+ * - NativeModules / Platform (@bsky.app/react-native-mmkv)
+ * Extend as new transitive usages appear.
+ */
+import {vi} from 'vitest'
+
+export const Image = {getSize: vi.fn()}
+
+export const NativeModules: Record<string, unknown> = {}
+
+export const Platform = {
+  OS: 'ios' as const,
+  select: <T>(o: {ios?: T; android?: T; native?: T; default?: T}): T =>
+    (o.ios ?? o.native ?? o.default) as T,
+}
+
+export const Dimensions = {
+  get: () => ({width: 390, height: 844, scale: 3, fontScale: 1}),
+  addEventListener: () => ({remove() {}}),
+}