Output a diff if there was only one call, but with wrong parameters

spec/core/matchers/toHaveBeenCalledOnceWithSpec.js

@@ -49,7 +49,7 @@ describe("toHaveBeenCalledOnceWith", function () {
     result = matcher.compare(calledSpy, 'a', 'b');
 
     expect(result.pass).toBe(false);
-    expect(result.message).toEqual("Expected spy called-spy to have been called only once, and with given args:\n  [ 'a', 'b' ]\nBut the actual calls were:\n  [ 'a', 'c' ].\n\n");
+    expect(result.message).toEqual("Expected spy called-spy to have been called only once, and with given args:\n  [ 'a', 'b' ]\nBut the actual call was:\n  [ 'a', 'c' ].\nExpected $[1] = 'c' to equal 'b'.\n\n");
   });
 
   it("fails when the actual was called multiple times with expected parameters", function () {

src/core/matchers/toHaveBeenCalledOnceWith.js

@@ -36,10 +36,23 @@ getJasmineRequireObj().toHaveBeenCalledOnceWith = function (j$) {
           };
         }
 
+        function getDiffs() {
+          return actual.calls.allArgs().map(function (argsForCall, callIx) {
+            var diffBuilder = new j$.DiffBuilder();
+            util.equals(argsForCall, expectedArgs, customEqualityTesters, diffBuilder);
+            return diffBuilder.getMessage();
+          });
+        }
+
         function butString() {
-          return actual.calls.count() !== 0
+          switch (actual.calls.count()) {
-            ? 'But the actual calls were:\n' + prettyPrintedCalls.join(',\n') + '.\n\n'
+            case 0:
-            : 'But it was never called.\n\n';
+              return 'But it was never called.\n\n';
+            case 1:
+              return 'But the actual call was:\n' + prettyPrintedCalls.join(',\n') + '.\n' + getDiffs().join('\n') + '\n\n';
+            default:
+              return 'But the actual calls were:\n' + prettyPrintedCalls.join(',\n') + '.\n\n';
+          }
         }
 
         return {