feat: add 'resetEnvironmentBetweenTestFiles' config property (#11)

This pull request adds a new configuration property that allows you to opt out of test file-based isolation and run multiple test files in a single JavaScript environment. This can speed up test execution at the cost of isolation, so if your tests modify the global context in any way, you should not enable it.

Author: V3RON

apps/playground/rn-harness.config.mjs

@@ -20,6 +20,8 @@ const config = {
   ],
   defaultRunner: 'android',
   bridgeTimeout: 120000,
+
+  resetEnvironmentBetweenTestFiles: true,
   unstable__skipAlreadyIncludedModules: false,
 };
 

packages/cli/src/commands/test.ts

@@ -103,7 +103,7 @@ const runTests = async (
   context: TestRunContext,
   options: TestFilterOptions = {}
 ): Promise<void> => {
-  const { bridge, environment, testFiles } = context;
+  const { bridge, environment, testFiles, config } = context;
   assert(bridge != null, 'Bridge not initialized');
   assert(environment != null, 'Environment not initialized');
   assert(testFiles != null, 'Test files not initialized');
@@ -141,7 +141,11 @@ const runTests = async (
 
     const result = await client.runTests(testFile, executionOptions);
     context.results = [...(context.results ?? []), ...result.suites];
-    shouldRestart = true;
+
+    if (config.resetEnvironmentBetweenTestFiles) {
+      shouldRestart = true;
+    }
+
     runSpinner.stop(`Test file ${testFile} completed`);
   }
 

packages/config/src/types.ts

@@ -81,6 +81,8 @@ export const ConfigSchema = z
       .number()
       .min(1000, 'Bridge timeout must be at least 1 second')
       .default(60000),
+
+    resetEnvironmentBetweenTestFiles: z.boolean().optional().default(true),
     unstable__skipAlreadyIncludedModules: z.boolean().optional().default(false),
   })
   .refine(

packages/jest/src/index.ts

@@ -73,6 +73,7 @@ export default class JestHarness implements CallbackTestRunnerInterface {
         tests,
         watcher,
         harness,
+        harnessConfig,
         onStart,
         onResult,
         onFailure
@@ -87,6 +88,7 @@ export default class JestHarness implements CallbackTestRunnerInterface {
     tests: Array<Test>,
     watcher: TestWatcher,
     harness: Harness,
+    harnessConfig: HarnessConfig,
     onStart: OnTestStart,
     onResult: OnTestSuccess,
     onFailure: OnTestFailure
@@ -103,7 +105,10 @@ export default class JestHarness implements CallbackTestRunnerInterface {
                 throw new CancelRun();
               }
 
-              if (!isFirstTest) {
+              if (
+                harnessConfig.resetEnvironmentBetweenTestFiles &&
+                !isFirstTest
+              ) {
                 await new Promise((resolve) => {
                   harness.bridge.once('ready', resolve);
                   harness.environment.restart();

website/src/docs/getting-started/configuration.mdx

@@ -89,6 +89,9 @@ AppRegistry.registerComponent('MyApp', () => App);
 
   // Optional: Bridge timeout in milliseconds (default: 60000)
   bridgeTimeout?: number;
+
+  // Optional: Reset environment between test files (default: true)
+  resetEnvironmentBetweenTestFiles?: boolean;
 }
 ```