test(metro-config): add tests for default config

.changeset/chatty-maps-teach.md

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+---
+---

packages/metro-config/test/__fixtures__/awesome-repo/node_modules/@react-native/community-cli-plugin/index.js

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+module.exports = {};

packages/metro-config/test/__fixtures__/awesome-repo/node_modules/@react-native/community-cli-plugin/package.json

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+{
+  "name": "@react-native/community-cli-plugin",
+  "version": "1000.0.0",
+  "description": "Core CLI commands for React Native",
+  "license": "MIT",
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/facebook/react-native.git",
+    "directory": "packages/community-cli-plugin"
+  },
+  "exports": {
+    ".": "./index.js",
+    "./package.json": "./package.json"
+  }
+}

packages/metro-config/test/__fixtures__/awesome-repo/node_modules/@react-native/metro-config/index.js

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+exports.getDefaultConfig = () => ({
+  resolver: {},
+  serializer: {},
+  transformer: {},
+});

packages/metro-config/test/__fixtures__/awesome-repo/node_modules/@react-native/metro-config/package.json

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+{
+  "name": "@react-native/metro-config",
+  "version": "1000.0.0",
+  "description": "Metro configuration for React Native",
+  "license": "MIT",
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/facebook/react-native.git"
+  },
+  "exports": {
+    ".": "./index.js",
+    "./package.json": "./package.json"
+  }
+}

packages/metro-config/test/__fixtures__/awesome-repo/node_modules/metro/index.js

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+module.exports = {};

packages/metro-config/test/__fixtures__/awesome-repo/node_modules/metro/package.json

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+{
+  "name": "metro",
+  "version": "1000.0.0",
+  "description": "🚇 The JavaScript bundler for React Native.",
+  "license": "MIT",
+  "repository": {
+    "type": "git",
+    "url": "[email protected]:facebook/metro.git"
+  },
+  "exports": {
+    ".": "./index.js",
+    "./package.json": "./package.json"
+  }
+}

packages/metro-config/test/__fixtures__/awesome-repo/node_modules/react-native-web/dist/modules/AssetRegistry/index.js

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+export function registerAsset() {}
+export function getAssetByID() {}

packages/metro-config/test/__fixtures__/awesome-repo/node_modules/react-native-web/package.json

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+{
+  "name": "react-native-web",
+  "version": "1000.0.0",
+  "description": "React Native for Web",
+  "license": "MIT",
+  "repository": {
+    "type": "git",
+    "url": "[email protected]:necolas/react-native-web.git"
+  }
+}

packages/metro-config/test/__fixtures__/awesome-repo/node_modules/react-native/package.json

@@ -6,5 +6,8 @@
   "repository": {
     "type": "git",
     "url": "[email protected]:facebook/react-native.git"
+  },
+  "dependencies": {
+    "@react-native/community-cli-plugin": "1000.0.0"
   }
 }

packages/metro-config/test/defaultConfig.test.ts

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+import { match, ok } from "node:assert";
+import { deepEqual, equal } from "node:assert/strict";
+import { describe, it } from "node:test";
+import { fileURLToPath } from "node:url";
+import { getDefaultConfig } from "../src/defaultConfig.js";
+
+describe("getDefaultConfig()", () => {
+  // @ts-expect-error Tests are run in ESM context
+  const thisFile = import.meta.url;
+
+  const projectRoot = fileURLToPath(
+    new URL("__fixtures__/awesome-repo/quaid", thisFile)
+  );
+
+  it("returns default Metro config", async () => {
+    const [config] = getDefaultConfig(projectRoot);
+    const { resolver, serializer, transformer } = config;
+
+    deepEqual(resolver?.platforms, ["android", "ios"]);
+    equal(typeof resolver.resolveRequest, "function");
+
+    const prelude = serializer?.getModulesRunBeforeMainModule?.(
+      fileURLToPath(thisFile)
+    );
+
+    ok(Array.isArray(prelude));
+    equal(prelude.length, 1);
+    match(prelude[0], /[/\\]Libraries[/\\]Core[/\\]InitializeCore.js$/);
+    ok(transformer);
+    ok(!transformer.assetRegistryPath);
+  });
+
+  it("returns config for web", async () => {
+    const [config] = getDefaultConfig(projectRoot, "web");
+    const { resolver, serializer, transformer } = config;
+
+    deepEqual(resolver?.platforms, ["android", "ios"]);
+    equal(typeof resolver.resolveRequest, "function");
+
+    const prelude = serializer?.getModulesRunBeforeMainModule?.(
+      fileURLToPath(thisFile)
+    );
+
+    ok(Array.isArray(prelude));
+    equal(prelude.length, 1);
+    match(prelude[0], /[/\\]Libraries[/\\]Core[/\\]InitializeCore.js$/);
+    ok(transformer);
+    match(
+      transformer.assetRegistryPath ?? "",
+      /node_modules[/\\]react-native-web[/\\]dist[/\\]modules[/\\]AssetRegistry[/\\]index.js$/
+    );
+  });
+});