Error checker util

package.json

@@ -1,6 +1,6 @@
 {
     "name": "@pocketgems/unit-test",
-    "version": "0.1.1",
+    "version": "0.2.0",
     "description": "A thin wrapper around Jest and Supertest to provide better organization",
     "main": "src/test.js",
     "scripts": {

src/test.js

@@ -2,6 +2,12 @@ if (Number(process.env.INDEBUGGER)) {
   jest.setTimeout(30 * 60 * 1000)
 }
 
+/**
+ * Helper error when attempting to examine contents of a given error.
+ * Should be used in conjunction with BaseServiceTest.prototype.getError
+ */
+class NoErrorThrownError extends Error {}
+
 class BaseTest {
   _listTestsOn (obj) {
     return Object.getOwnPropertyNames(obj).filter(name => {
@@ -41,6 +47,25 @@ class BaseTest {
   async beforeEach () {}
   async afterEach () {}
 
+   /**
+   * Catches error from specified call. Error may be examined by calling
+   * tests.
+   * This approach is recommended for in-depth assertions on errors:
+   * https://github.com/jest-community/eslint-plugin-jest/blob/main/docs/rules/no-conditional-expect.md#how-to-catch-a-thrown-error-for-testing-without-violating-this-rule
+   * @param {Promise} call - function expected to throw
+   * @throws {NoErrorThrownError} - exception if 'call' method
+   * does not throw.
+   * @returns {Error} error thrown be inner call method.
+   */
+   async catchError (call) {
+    try {
+      await call()
+    } catch (error) {
+      return error
+    }
+    throw new NoErrorThrownError()
+  }
+
   runTests () {
     describe(this.constructor.name, () => {
       beforeAll(async () => {

test/unit-test-example.js

@@ -1,6 +1,13 @@
 const { Example } = require('../example/feature')
 const { BaseTest, runTests } = require('../src/test')
 
+class CustomError extends Error {
+  constructor(message, customData) {
+    super(message)
+    this.customData = customData
+  }
+}
+
 class ExampleTest extends BaseTest {
   testMultiply () {
     expect(Example.multiply(2, 3)).toBe(6)
@@ -9,6 +16,25 @@ class ExampleTest extends BaseTest {
   testInvalidCall () {
     expect(() => Example.broken()).toThrow()
   }
+
+  async testCatchError () {
+    const shouldThrow = () => {
+      throw new CustomError('hello!', {
+        a: 33,
+        b: [1,2]
+      })
+    }
+    const error = await this.catchError(shouldThrow)
+    expect(error).toBeInstanceOf(CustomError)
+    expect(error.message).toEqual('hello!')
+    expect(error.customData).toEqual({
+      a: 33,
+      b: [1,2]
+    })
+    const doesNotThrow = () => 2
+    await expect(this.catchError(doesNotThrow))
+      .rejects.toThrow()
+  }
 }
 
 runTests(ExampleTest)