Merge pull request #157 from storybookjs/feat/add-console-logs-on-fai…

…lure

feat: add console logs on test failure

src/setup-page.ts

@@ -50,26 +50,70 @@ export const setupPage = async (page) => {
 
   await page.addScriptTag({
     content: `
+      // colorizes the console output
+      const bold = (message) => \`\\u001b[1m\${message}\\u001b[22m\`;
+      const magenta = (message) => \`\\u001b[35m\${message}\\u001b[39m\`;
+      const blue = (message) => \`\\u001b[34m\${message}\\u001b[39m\`;
+      const red = (message) => \`\\u001b[31m\${message}\\u001b[39m\`;
+      const yellow = (message) => \`\\u001b[33m\${message}\\u001b[39m\`;
+      
+      // removes circular references from the object
+      function serializer(replacer, cycleReplacer) {
+        let stack = [],
+          keys = [];
+
+        if (cycleReplacer == null)
+          cycleReplacer = function (_key, value) {
+            if (stack[0] === value) return '[Circular]';
+            return '[Circular ~.' + keys.slice(0, stack.indexOf(value)).join('.') + ']';
+          };
+
+        return function (key, value) {
+          if (stack.length > 0) {
+            let thisPos = stack.indexOf(this);
+            ~thisPos ? stack.splice(thisPos + 1) : stack.push(this);
+            ~thisPos ? keys.splice(thisPos, Infinity, key) : keys.push(key);
+            if (~stack.indexOf(value)) value = cycleReplacer.call(this, key, value);
+          } else {
+            stack.push(value);
+          }
+
+          return replacer == null ? value : replacer.call(this, key, value);
+        };
+      }
+
+      function safeStringify(obj, replacer, spaces, cycleReplacer) {
+        return JSON.stringify(obj, serializer(replacer, cycleReplacer), spaces);
+      }
+
+      function composeMessage(args) {
+        if (typeof args === 'undefined') return "undefined";
+        if (typeof args === 'string') return args;
+        return safeStringify(args);
+      }
+
       function truncate(input, limit) {
         if (input.length > limit) {
           return input.substring(0, limit) + '…';
         }
         return input;
       }
-
+      
       class StorybookTestRunnerError extends Error {
-        constructor(storyId, errorMessage) {
+        constructor(storyId, errorMessage, logs) {
           super(errorMessage);
           this.name = 'StorybookTestRunnerError';
           const storyUrl = \`${referenceURL || targetURL}?path=/story/\${storyId}\`;
           const finalStoryUrl = \`\${storyUrl}&addonPanel=storybook/interactions/panel\`;
+          const separator = '\\n\\n--------------------------------------------------';
+          const extraLogs = logs.length > 0 ? separator + "\\n\\nBrowser logs:\\n\\n"+ logs.join('\\n\\n') : '';
 
-          this.message = \`\nAn error occurred in the following story. Access the link for full output:\n\${finalStoryUrl}\n\nMessage:\n \${truncate(errorMessage,${debugPrintLimit})}\`;
+          this.message = \`\nAn error occurred in the following story. Access the link for full output:\n\${finalStoryUrl}\n\nMessage:\n \${truncate(errorMessage,${debugPrintLimit})}\n\${extraLogs}\`;
         }
       }
 
-      async function __throwError(storyId, errorMessage) {
-        throw new StorybookTestRunnerError(storyId, errorMessage);
+      async function __throwError(storyId, errorMessage, logs) {
+        throw new StorybookTestRunnerError(storyId, errorMessage, logs);
       }
 
       async function __waitForElement(selector) {
@@ -118,18 +162,45 @@ export const setupPage = async (page) => {
             'The test runner could not access the Storybook channel. Are you sure the Storybook is running correctly in that URL?'
           );
         }
+        
+        // collect logs to show upon test error
+        let logs = [];
+
+        const spyOnConsole = (method, name) => {
+          const originalFn = console[method];
+          return function () {
+            const message = [...arguments].map(composeMessage).join(', ');
+            const prefix = \`\${bold(name)}: \`;
+            logs.push(prefix + message);
+            originalFn.apply(console, arguments);
+          };
+        };
+
+        // console methods + color function for their prefix
+        const spiedMethods = {
+          log: blue,
+          warn: yellow,
+          error: red,
+          trace: magenta,
+          group: magenta,
+          groupCollapsed: magenta,
+        }
+        
+        Object.entries(spiedMethods).forEach(([method, color]) => {
+          console[method] = spyOnConsole(method, color(method))
+        })
 
         return new Promise((resolve, reject) => {
           channel.on('${renderedEvent}', () => resolve(document.getElementById('root')));
           channel.on('storyUnchanged', () => resolve(document.getElementById('root')));
           channel.on('storyErrored', ({ description }) => reject(
-            new StorybookTestRunnerError(storyId, description))
+            new StorybookTestRunnerError(storyId, description, logs))
           );
           channel.on('storyThrewException', (error) => reject(
-            new StorybookTestRunnerError(storyId, error.message))
+            new StorybookTestRunnerError(storyId, error.message, logs))
           );
           channel.on('storyMissing', (id) => id === storyId && reject(
-            new StorybookTestRunnerError(storyId, 'The story was missing when trying to access it.'))
+            new StorybookTestRunnerError(storyId, 'The story was missing when trying to access it.', logs))
           );
 
           channel.emit('setCurrentStory', { storyId, viewMode: '${viewMode}' });