improve expectRevert output

src/expectRevert.js

@@ -1,4 +1,5 @@
 const { web3 } = require('./setup');
+const { expect } = require('chai');
 
 const colors = require('ansi-colors');
 const semver = require('semver');
@@ -8,12 +9,13 @@ async function expectException (promise, expectedError) {
     await promise;
   } catch (error) {
     if (error.message.indexOf(expectedError) === -1) {
-      throw Error(`Wrong failure type, expected '${expectedError}' and got '${error.message}'`);
+      const actualError = error.message.replace('Returned error: VM Exception while processing transaction: ', '');
+      expect.fail(actualError, expectedError, 'Wrong kind of exception received');
     }
     return;
   }
 
-  throw Error('Expected failure not received');
+  expect.fail('Expected an exception but none was received');
 }
 
 const expectRevert = async function (promise, expectedError) {

test/helpers/assertFailure.js

@@ -4,7 +4,7 @@ async function assertFailure (promise) {
   try {
     await promise;
   } catch (error) {
-    return;
+    return error;
   }
   expect.fail();
 }

test/src/expectRevert.test.js

@@ -1,3 +1,5 @@
+const { expect } = require('chai');
+
 const assertFailure = require('../helpers/assertFailure');
 const expectRevert = require('../../src/expectRevert');
 
@@ -10,7 +12,10 @@ describe('expectRevert', function () {
 
   describe('expectRevert', function () {
     it('rejects if no revert occurs', async function () {
-      await assertFailure(expectRevert(this.reverter.dontRevert()));
+      const assertion =
+        await assertFailure(expectRevert(this.reverter.dontRevert(), 'reason'));
+
+      expect(assertion.message).to.equal('Expected an exception but none was received');
     });
 
     it('rejects a revert', async function () {
@@ -22,7 +27,10 @@ describe('expectRevert', function () {
     });
 
     it('rejects a revert with incorrect expected reason', async function () {
-      await assertFailure(expectRevert(this.reverter.revertFromRevertWithReason(), 'Wrong reason'));
+      const assertion =
+        await assertFailure(expectRevert(this.reverter.revertFromRevertWithReason(), 'Wrong reason'));
+
+      expect(assertion.message).to.equal('Wrong kind of exception received');
     });
 
     it('accepts a revert with correct expected reason', async function () {