Fixes #4 Improve error reporting

__tests__/ErrorMessage.test.ts

@@ -0,0 +1,35 @@
+import { ErrorMessage } from "../src/ErrorMessage"
+
+describe('ErrorMessage', () => {
+    it('generates message with errors', () => {
+        const resource = "release"
+        const error = {
+            message: 'something bad happened',
+            errors: [
+                {
+                    code: 'missing',
+                    resource: 'release'
+                },
+                {
+                    code: 'already_exists',
+                    resource: 'release'
+                }
+            ]
+        }
+
+        const errorMessage = new ErrorMessage(error)
+
+        const expectedString = "something bad happened\nErrors:\n- release does not exist.\n- release already exists."
+        expect(errorMessage.toString()).toBe(expectedString)
+    })
+
+    it('generates message without errors', () => {
+        const error = {
+            message: 'something bad happened'
+        }
+
+        const errorMessage = new ErrorMessage(error)
+
+        expect(errorMessage.toString()).toBe('something bad happened')
+    })
+})