Fix bugs with error diff calculation

lib/reporter/base.js

@@ -126,8 +126,15 @@ const GlaceReporter = function (runner) {
     runner.on("fail", (mochaTest, err) => {
 
         if (err.actual && err.expected) {
-            err.diff = colors.strip(
-                MochaReporter.generateDiff(err.actual, err.expected));
+            try {
+                err.diff = colors.strip(
+                    MochaReporter.generateDiff(err.actual, err.expected));
+                if (err.diff.trim() === "+ expected - actual") {
+                    delete err.diff;
+                }
+            } catch (e) {
+                /* do nothing */
+            }
         }
         utils.accountError(mochaTest.title, err);
 

tests/unit/testGlobals.js

@@ -8,6 +8,25 @@ suite("globals", () => {
         sandbox.restore();
     });
 
+    test("chai", () => {
+        let chai = require("chai"),
+            threshold = chai.config.truncateThreshold;
+
+        beforeChunk(() => {
+            CONF.report.deepErrors = true;
+        });
+
+        afterChunk(() => {
+            CONF.report.deepErrors = false;
+            chai.config.truncateThreshold = threshold;
+        });
+
+        chunk("shows full objects in errors", () => {
+            rewire("../../lib/globals");
+            expect(chai.config.truncateThreshold).to.be.equal(0);
+        });
+    });
+
     test("chai as promised", () => {
 
         chunk("checks fulfilled promise", async () => {

tests/unit/testReporterBase.js

@@ -9,11 +9,11 @@ const runner = {
 };
 
 suite("reporter/base", () => {
-    let glaceReporter;
+    let glaceReporter, MochaReporter;
     const sandbox = sinon.createSandbox();
 
     beforeChunk(() => {
-        const MochaReporter = function () {};
+        MochaReporter = function () {};
         MochaReporter.generateDiff = () => "";
         GlaceReporter.__set__("MochaReporter", MochaReporter);
         glaceReporter = new GlaceReporter(runner);
@@ -393,6 +393,18 @@ suite("reporter/base", () => {
             reporters.push({});
             onFail({ title: "my chunk" }, "error");
         });
+
+        chunk("does not add diff if it is empty", () => {
+            MochaReporter.generateDiff = () => "+ expected - actual";
+            reporters.push({ fail: sinon.spy() });
+            onFail({ title: "my chunk" },
+                { actual: "{\n\"a\": 1}", expected: "{\n\"b\": 1}" });
+
+            expect(accountError).to.be.calledOnce;
+            expect(accountError.args[0][0]).to.be.equal("my chunk");
+            expect(accountError.args[0][1]).to.be
+                .eql({ actual: "{\n\"a\": 1}", expected: "{\n\"b\": 1}" });
+        });
     });
 
     test("on pending", () => {