single expect per test assertion

Co-authored-by: Sebastian "Sebbie" Silbermann <sebastian.silbermann@vercel.com>

Author: devjiwonchoi

test/development/typescript-plugin/metadata/warn-no-type.test.ts

@@ -1,12 +1,18 @@
 import type { PluginLanguageService } from '../test-utils'
 
-import { join } from 'node:path'
+import ts from 'typescript'
+import { join, relative } from 'node:path'
 import {
   getPluginLanguageService,
   getTsFiles,
   NEXT_TS_ERRORS,
 } from '../test-utils'
 
+type PartialDiagnostic = Pick<
+  ts.Diagnostic,
+  'code' | 'messageText' | 'start' | 'length'
+>
+
 const fixturesDir = join(__dirname, 'app/warn-no-type')
 
 describe('typescript-plugin - metadata - warn-no-type', () => {
@@ -20,66 +26,109 @@ describe('typescript-plugin - metadata - warn-no-type', () => {
     const hasTypeDir = join(fixturesDir, 'metadata', 'has-type')
     const tsFiles = getTsFiles(hasTypeDir)
 
+    const expectedDiagnostics = new Map<string, PartialDiagnostic[]>()
+    const totalDiagnostics = new Map<string, PartialDiagnostic[]>()
+
     for (const tsFile of tsFiles) {
-      const diagnostics = languageService.getSemanticDiagnostics(tsFile)
-      expect({ diagnostics, tsFile }).toEqual({ diagnostics: [], tsFile })
+      const relativePath = relative(__dirname, tsFile)
+      // When the test fails, comparing diagnostics to an empty array using
+      // toEqual() results in terminal output that is too long and omits the
+      // filename. Therefore, we filter out only the important properties.
+      const diagnostics = languageService
+        .getSemanticDiagnostics(tsFile)
+        .map((diagnostic) => ({
+          code: diagnostic.code,
+          messageText: diagnostic.messageText,
+          start: diagnostic.start,
+          length: diagnostic.length,
+        }))
+
+      expectedDiagnostics.set(relativePath, [])
+      totalDiagnostics.set(relativePath, diagnostics)
     }
+
+    expect(totalDiagnostics).toEqual(expectedDiagnostics)
   })
 
   it('should not have diagnostics for generateMetadata with type', () => {
     const hasTypeDir = join(fixturesDir, 'generate-metadata', 'has-type')
     const tsFiles = getTsFiles(hasTypeDir)
 
+    const expectedDiagnostics = new Map<string, PartialDiagnostic[]>()
+    const totalDiagnostics = new Map<string, PartialDiagnostic[]>()
+
     for (const tsFile of tsFiles) {
-      const diagnostics = languageService.getSemanticDiagnostics(tsFile)
-      expect({ diagnostics, tsFile }).toEqual({ diagnostics: [], tsFile })
+      const relativePath = relative(__dirname, tsFile)
+      // When the test fails, comparing diagnostics to an empty array using
+      // toEqual() results in terminal output that is too long and omits the
+      // filename. Therefore, we filter out only the important properties.
+      const diagnostics = languageService
+        .getSemanticDiagnostics(tsFile)
+        .map((diagnostic) => ({
+          code: diagnostic.code,
+          messageText: diagnostic.messageText,
+          start: diagnostic.start,
+          length: diagnostic.length,
+        }))
+
+      expectedDiagnostics.set(relativePath, [])
+      totalDiagnostics.set(relativePath, diagnostics)
     }
+
+    expect(totalDiagnostics).toEqual(expectedDiagnostics)
   })
 
   it('should have diagnostics for metadata with no type', () => {
     const noTypeDir = join(fixturesDir, 'metadata', 'no-type')
     const tsFiles = getTsFiles(noTypeDir)
 
+    const expectedDiagnostics = new Map<string, PartialDiagnostic[]>()
+    const totalDiagnostics = new Map<string, PartialDiagnostic[]>()
+
     for (const tsFile of tsFiles) {
+      const relativePath = relative(__dirname, tsFile)
       const diagnostics = languageService.getSemanticDiagnostics(tsFile)
 
-      expect({ diagnostics, tsFile }).toEqual({
-        diagnostics: [
-          expect.objectContaining({
-            code: NEXT_TS_ERRORS.INVALID_METADATA_EXPORT,
-            messageText:
-              'The Next.js "metadata" export should be type of "Metadata" from "next".',
-            start: diagnostics[0].file.getFullText().lastIndexOf('metadata'),
-            length: 'metadata'.length,
-          }),
-        ],
-        tsFile,
-      })
+      expectedDiagnostics.set(relativePath, [
+        expect.objectContaining({
+          code: NEXT_TS_ERRORS.INVALID_METADATA_EXPORT,
+          messageText:
+            'The Next.js "metadata" export should be type of "Metadata" from "next".',
+          // Use lastIndexOf to match export { ... }
+          start: ts.sys.readFile(tsFile).lastIndexOf('metadata'),
+          length: 'metadata'.length,
+        }),
+      ])
+      totalDiagnostics.set(relativePath, diagnostics)
     }
+
+    expect(totalDiagnostics).toEqual(expectedDiagnostics)
   })
 
   it('should have diagnostics for generateMetadata with no type', () => {
     const noTypeDir = join(fixturesDir, 'generate-metadata', 'no-type')
     const tsFiles = getTsFiles(noTypeDir)
 
+    const expectedDiagnostics = new Map<string, PartialDiagnostic[]>()
+    const totalDiagnostics = new Map<string, PartialDiagnostic[]>()
+
     for (const tsFile of tsFiles) {
+      const relativePath = relative(__dirname, tsFile)
       const diagnostics = languageService.getSemanticDiagnostics(tsFile)
       const type = tsFile.includes('-async-') ? 'Promise<Metadata>' : 'Metadata'
 
-      expect({ diagnostics, tsFile }).toEqual({
-        diagnostics: [
-          expect.objectContaining({
-            code: NEXT_TS_ERRORS.INVALID_METADATA_EXPORT,
-            messageText: `The Next.js "generateMetadata" export should have a return type of "${type}" from "next".`,
-            // Use lastIndexOf to match export { ... }
-            start: diagnostics[0].file
-              .getFullText()
-              .lastIndexOf('generateMetadata'),
-            length: 'generateMetadata'.length,
-          }),
-        ],
-        tsFile,
-      })
+      expectedDiagnostics.set(relativePath, [
+        expect.objectContaining({
+          code: NEXT_TS_ERRORS.INVALID_METADATA_EXPORT,
+          messageText: `The Next.js "generateMetadata" export should have a return type of "${type}" from "next".`,
+          // Use lastIndexOf to match export { ... }
+          start: ts.sys.readFile(tsFile).lastIndexOf('generateMetadata'),
+          length: 'generateMetadata'.length,
+        }),
+      ])
+      totalDiagnostics.set(relativePath, diagnostics)
     }
+
+    expect(totalDiagnostics).toEqual(expectedDiagnostics)
   })
 })