test: add unit test for define plugin

packages/vite/src/node/__tests__/plugins/define.spec.ts

@@ -0,0 +1,39 @@
+import { definePlugin } from '../../plugins/define'
+import { resolveConfig } from '../../config'
+
+async function createDefinePluginTransform(
+  define: Record<string, any> = {},
+  build = true,
+  ssr = false
+) {
+  const config = await resolveConfig({ define }, build ? 'build' : 'serve')
+  const instance = definePlugin(config)
+  return async (code: string) => {
+    const result = await instance.transform.call({}, code, 'foo.ts', { ssr })
+    return result?.code || result
+  }
+}
+
+describe('definePlugin', () => {
+  test('replaces custom define', async () => {
+    const transform = await createDefinePluginTransform({
+      __APP_VERSION__: JSON.stringify('1.0')
+    })
+    expect(await transform('const version = __APP_VERSION__ ;')).toBe(
+      'const version = "1.0" ;'
+    )
+    expect(await transform('const version = __APP_VERSION__;')).toBe(
+      'const version = "1.0";'
+    )
+  })
+
+  test('replaces import.meta.env.SSR with false', async () => {
+    const transform = await createDefinePluginTransform()
+    expect(await transform('const isSSR = import.meta.env.SSR ;')).toBe(
+      'const isSSR = false ;'
+    )
+    expect(await transform('const isSSR = import.meta.env.SSR;')).toBe(
+      'const isSSR = false;'
+    )
+  })
+})