test_runner: support mocking json modules

PR-URL: #58007
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Pietro Marchini <pietro.marchini94@gmail.com>
Reviewed-By: Marco Ippolito <marcoippolito54@gmail.com>
Reviewed-By: Chemi Atlow <chemi@atlow.co.il>
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>

Author: JakobJingleheimer

doc/api/test.md

@@ -2168,6 +2168,11 @@ test('spies on an object method', (t) => {
 added:
  - v22.3.0
  - v20.18.0
+changes:
+ - version:
+ - REPLACEME
+ pr-url: https://github.com/nodejs/node/pull/58007
+ description: Support JSON modules.
 -->
 
 > Stability: 1.0 - Early development
@@ -2191,10 +2196,10 @@ added:
  mock will throw an exception when used as a CJS or builtin module.
 * Returns: {MockModuleContext} An object that can be used to manipulate the mock.
 
-This function is used to mock the exports of ECMAScript modules, CommonJS
-modules, and Node.js builtin modules. Any references to the original module
-prior to mocking are not impacted. In order to enable module mocking, Node.js must
-be started with the [`--experimental-test-module-mocks`][] command-line flag.
+This function is used to mock the exports of ECMAScript modules, CommonJS modules, JSON modules, and
+Node.js builtin modules. Any references to the original module prior to mocking are not impacted. In
+order to enable module mocking, Node.js must be started with the
+[`--experimental-test-module-mocks`][] command-line flag.
 
 The following example demonstrates how a mock is created for a module.
 

lib/internal/test_runner/mock/loader.js

@@ -118,10 +118,17 @@ async function load(url, context, nextLoad) {
 // Treat builtins as commonjs because customization hooks do not allow a
 // core module to be replaced.
 // Also collapse 'commonjs-sync' and 'require-commonjs' to 'commonjs'.
-constformat=(
-original.format==='builtin'||
-original.format==='commonjs-sync'||
-original.format==='require-commonjs') ? 'commonjs' : original.format;
+letformat=original.format;
+switch(original.format){
+case'builtin': // Deliberate fallthrough
+case'commonjs-sync': // Deliberate fallthrough
+case'require-commonjs':
+format='commonjs';
+break;
+case'json':
+format='module';
+break;
+}
 
 constresult={
 __proto__: null,

lib/internal/test_runner/mock/mock.js

@@ -70,7 +70,14 @@ const kMockUnknownMessage = 3;
 constkWaitTimeout=5_000;
 constkBadExportsMessage='Cannot create mock because named exports '+
 'cannot be applied to the provided default export.';
-constkSupportedFormats=['builtin','commonjs','module','module-typescript','commonjs-typescript'];
+constkSupportedFormats=[
+'builtin',
+'commonjs-typescript',
+'commonjs',
+'json',
+'module-typescript',
+'module',
+];
 letsharedModuleState;
 
 classMockFunctionContext{

test/fixtures/module-mocking/basic.json

@@ -0,0 +1 @@
+{"foo":"bar"}

test/parallel/test-runner-module-mocking.js

@@ -365,6 +365,34 @@ test('ESM mocking with namedExports option', async (t) => {
 });
 });
 
+test('JSON mocking',async(t)=>{
+awaitt.test('with defaultExport',async(t)=>{
+constfixturePath=fixtures.path('module-mocking','basic.json');
+constfixture=pathToFileURL(fixturePath);
+const{default: original}=awaitimport(fixture,{with: {type: 'json'}});
+
+assert.deepStrictEqual(original,{foo: 'bar'});
+
+constdefaultExport={qux: 'zed'};
+
+t.mock.module(fixture,{ defaultExport });
+
+const{default: mocked}=awaitimport(fixture,{with: {type: 'json'}});
+
+assert.deepStrictEqual(mocked,defaultExport);
+});
+
+awaitt.test('throws without appropriate import attributes',async(t)=>{
+constfixturePath=fixtures.path('module-mocking','basic.json');
+constfixture=pathToFileURL(fixturePath);
+
+constdefaultExport={qux: 'zed'};
+t.mock.module(fixture,{ defaultExport });
+
+awaitassert.rejects(()=>import(fixture),/importattribute/);
+});
+});
+
 test('modules cannot be mocked multiple times at once',async(t)=>{
 awaitt.test('CJS',async(t)=>{
 constfixture=fixtures.path('module-mocking','basic-cjs.js');