fix(storybook): only add @storybook/test-runner to externalDependenci…

…es if installed (#28060)

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## Current Behavior
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Fixes #26854

packages/storybook/src/plugins/plugin.spec.ts

@@ -82,7 +82,7 @@ describe('@nx/storybook/plugin', () => {
       inputs: [
         'production',
         '^production',
-        { externalDependencies: ['storybook', '@storybook/test-runner'] },
+        { externalDependencies: ['storybook'] },
       ],
     });
     expect(
@@ -136,11 +136,7 @@ describe('@nx/storybook/plugin', () => {
         'production',
         '^production',
         {
-          externalDependencies: [
-            'storybook',
-            '@storybook/angular',
-            '@storybook/test-runner',
-          ],
+          externalDependencies: ['storybook', '@storybook/angular'],
         },
       ],
     });
@@ -200,7 +196,7 @@ describe('@nx/storybook/plugin', () => {
       inputs: [
         'production',
         '^production',
-        { externalDependencies: ['storybook', '@storybook/test-runner'] },
+        { externalDependencies: ['storybook'] },
       ],
     });
     expect(

packages/storybook/src/plugins/plugin.ts

@@ -187,7 +187,9 @@ function buildTarget(
           externalDependencies: [
             'storybook',
             '@storybook/angular',
-            '@storybook/test-runner',
+            isStorybookTestRunnerInstalled()
+              ? '@storybook/test-runner'
+              : undefined,
           ],
         },
       ],
@@ -203,7 +205,12 @@ function buildTarget(
           ? ['production', '^production']
           : ['default', '^default']),
         {
-          externalDependencies: ['storybook', '@storybook/test-runner'],
+          externalDependencies: [
+            'storybook',
+            isStorybookTestRunnerInstalled()
+              ? '@storybook/test-runner'
+              : undefined,
+          ],
         },
       ],
     };
@@ -241,7 +248,12 @@ function testTarget(projectRoot: string) {
     options: { cwd: projectRoot },
     inputs: [
       {
-        externalDependencies: ['storybook', '@storybook/test-runner'],
+        externalDependencies: [
+          'storybook',
+          isStorybookTestRunnerInstalled()
+            ? '@storybook/test-runner'
+            : undefined,
+        ],
       },
     ],
   };