feat: added stderr matcher

Closes #9

Author: crutchcorn

package.json

@@ -43,6 +43,7 @@
     "jest-matcher-utils": "^27.4.2",
     "lz-string": "^1.4.4",
     "pretty-format": "^27.0.2",
+    "redent": "^3.0.0",
     "strip-ansi": "^6.0.1",
     "strip-final-newline": "^2.0.0",
     "tree-kill": "^1.2.2"

src/__tests__/matchers.js

@@ -1,5 +1,6 @@
 const {resolve} = require('path')
 const {render} = require('../pure')
+const {toHaveErrorMessage} = require("../matchers/to-have-errormessage");
 
 test('toBeInTheConsole should pass when something is in console', async () => {
   const {findByText} = await render('node', [
@@ -20,3 +21,41 @@ test('toBeInTheConsole should fail when something is not console', async () => {
 
   expect(() => expect(queryByText('NotHere')).toBeInTheConsole()).toThrow(/value must be a TestInstance/)
 })
+
+test('toHaveErrorMessage should pass during stderr when no string passed', async () => {
+  const instance = await render('node', [
+    resolve(__dirname, './execute-scripts/throw.js'),
+  ])
+
+  await expect(
+      (async () => expect(instance).toHaveErrorMessage())()
+  ).resolves.not.toThrow()
+})
+
+test('toHaveErrorMessage should pass during stderr when string passed', async () => {
+  const instance = await render('node', [
+    resolve(__dirname, './execute-scripts/throw.js'),
+  ])
+
+  await expect(
+      (async () => expect(instance).toHaveErrorMessage(/Search for this error in stderr/))()
+  ).resolves.not.toThrow()
+})
+
+test('toHaveErrorMessage should fail when something is not in stderr', async () => {
+  const {queryByText} = await render('node', [
+    resolve(__dirname, './execute-scripts/list-args.js'),
+    '--version',
+  ])
+
+  expect(() => expect(queryByText('--version')).toHaveErrorMessage("Error isn't here")).toThrow(/Expected the element to have error message/)
+})
+
+test('toHaveErrorMessage should fail when null is passed', async () => {
+  const {queryByText} = await render('node', [
+    resolve(__dirname, './execute-scripts/list-args.js'),
+    '--version',
+  ])
+
+  expect(() => expect(queryByText('NotHere')).toHaveErrorMessage()).toThrow(/value must be a TestInstance/)
+})

src/matchers/index.js

@@ -1,5 +1,7 @@
 import {toBeInTheConsole} from './to-be-in-the-console'
+import {toHaveErrorMessage} from './to-have-errormessage'
 
 export {
-    toBeInTheConsole
+    toBeInTheConsole,
+    toHaveErrorMessage
 }

src/matchers/to-be-in-the-console.js

@@ -1,9 +1,8 @@
+/* eslint-disable @babel/no-invalid-this */
 import {checkCliInstance} from "./utils";
 
 export function toBeInTheConsole(instance) {
-  // eslint-disable-next-line @babel/no-invalid-this
   if (instance !== null || !this.isNot) {
-    // eslint-disable-next-line @babel/no-invalid-this
     checkCliInstance(instance, toBeInTheConsole, this)
   }
 

src/matchers/to-have-errormessage.js

@@ -0,0 +1,39 @@
+/* eslint-disable @babel/no-invalid-this */
+import {getDefaultNormalizer} from "../matches";
+import {checkCliInstance, getMessage} from './utils'
+
+/**
+ * @param {TestInstance} testInstance
+ * @param checkWith
+ */
+export function toHaveErrorMessage(testInstance, checkWith) {
+    checkCliInstance(testInstance, toHaveErrorMessage, this)
+
+    const expectsErrorMessage = checkWith !== undefined
+
+    const errormessage = getDefaultNormalizer()(testInstance.stderrArr.join('\n'))
+
+    return {
+        pass: expectsErrorMessage
+            ? checkWith instanceof RegExp
+                ? checkWith.test(errormessage)
+                : this.equals(errormessage, checkWith)
+            : Boolean(testInstance.stderrArr.length),
+        message: () => {
+            const to = this.isNot ? 'not to' : 'to'
+            return getMessage(
+                this,
+                this.utils.matcherHint(
+                    `${this.isNot ? '.not' : ''}.toHaveErrorMessage`,
+                    'element',
+                    '',
+                ),
+                `Expected the element ${to} have error message`,
+                this.utils.printExpected(checkWith),
+                'Received',
+                this.utils.printReceived(errormessage),
+            )
+        },
+    }
+
+}

src/matchers/utils.js

@@ -1,3 +1,5 @@
+import redent from 'redent'
+
 class GenericTypeError extends Error {
     constructor(expectedString, received, matcherFn, context) {
         super()
@@ -51,7 +53,33 @@ function checkCliInstance(cliInstance, ...args) {
     }
 }
 
+function display(context, value) {
+    return typeof value === 'string' ? value : context.utils.stringify(value)
+}
+
+function getMessage(
+    context,
+    matcher,
+    expectedLabel,
+    expectedValue,
+    receivedLabel,
+    receivedValue,
+) {
+    return [
+        `${matcher}\n`,
+        // eslint-disable-next-line @babel/new-cap
+        `${expectedLabel}:\n${context.utils.EXPECTED_COLOR(
+            redent(display(context, expectedValue), 2),
+        )}`,
+        // eslint-disable-next-line @babel/new-cap
+        `${receivedLabel}:\n${context.utils.RECEIVED_COLOR(
+            redent(display(context, receivedValue), 2),
+        )}`,
+    ].join('\n')
+}
+
 export {
     CliInstanceTypeError,
     checkCliInstance,
+    getMessage
 }

types/extend-expect.d.ts

@@ -6,10 +6,17 @@ declare namespace jest {
     interface Matchers<R, ignored> {
         /**
          * @description
-         * Assert whether an element is present in the console or not.
+         * Assert whether a query is present in the console or not.
          * @example
          * expect(queryByText('Hello world')).toBeInTheDocument()
          */
         toBeInTheConsole(): R;
+        /**
+         * @description
+         * Check whether the given instance has an stderr message or not.
+         * @example
+         * expect(instance).toHaveErrorMessage(/command could not be found/i) // to partially match
+         */
+        toHaveErrorMessage(): R;
     }
 }