Expose inner error message alongside consumer provided message (#2)

package.json

@@ -32,7 +32,7 @@
     "babel-minify": "0.5.0",
     "babel-preset-env": "1.7.0",
     "documentation": "9.1.1",
-    "eslint": "5.12.0",
+    "eslint": "5.12.1",
     "is-docker": "1.1.0",
     "istanbul": "0.4.5",
     "istanbul-instrumenter-loader": "3.0.1",

src/index.js

@@ -15,6 +15,6 @@ export default function coerce (value, Type, message) {
         return new Type(value);
     }
     catch (error) {
-        throw new TypeError(message);
+        throw new TypeError(`${message} Inner Error: ${error.message}`);
     }
 }

src/index.spec.js

@@ -1,9 +1,10 @@
 import coerce from './index';
 
+const ERROR_MESSAGE = 'You failing the hardest';
 class FakeClassForTesting {}
 class FailingClassForTesting {
     constructor() {
-        throw new Error('You failing the hardest');
+        throw new Error(ERROR_MESSAGE);
     }
 }
 describe('coerce', () => {
@@ -26,6 +27,14 @@ describe('coerce', () => {
     it('should cast into the type and return Typed version', () => {
         const errorMessage = 'south things have gone';
 
-        expect(() => coerce({}, FailingClassForTesting, errorMessage)).toThrowError(errorMessage);
+        const errorMessageRegex = new RegExp(`${errorMessage}`);
+        expect(() => coerce({}, FailingClassForTesting, errorMessage)).toThrowError(errorMessageRegex);
+    });
+
+    it('should add inner message to error message', () => {
+        const errorMessage = 'south things have gone';
+
+        const errorMessageRegex = new RegExp(`${errorMessage}.*${ERROR_MESSAGE}`);
+        expect(() => coerce({}, FailingClassForTesting, errorMessage)).toThrowError(errorMessageRegex);
     });
 });