add throwsArg(index) to stubs

This was requested through sinonjs#1270
seppevs · Mar 8, 2017 · 32757dc · 32757dc
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diff --git a/docs/_releases/v1.17.6/stubs.md b/docs/_releases/v1.17.6/stubs.md
@@ -219,6 +219,12 @@ Causes the stub to throw an exception of the provided type.
 
 Causes the stub to throw the provided exception object.
 
+#### `stub.throwsArg(index);`
+
+Causes the stub to throw the argument exception at the provided index.
+
+`stub.returnsArg(0);` causes the stub to throw the first argument exception.
+
 
 #### `stub.callsArg(index);`
 

diff --git a/lib/sinon/behavior.js b/lib/sinon/behavior.js
@@ -113,6 +113,7 @@ var proto = {
                 this.exception ||
                 typeof this.returnArgAt === "number" ||
                 this.returnThis ||
+                typeof this.throwArgAt === "number" ||
                 this.fakeFn ||
                 this.returnValueDefined);
     },
@@ -126,6 +127,8 @@ var proto = {
             return args[this.returnArgAt];
         } else if (this.returnThis) {
             return context;
+        } else if (typeof this.throwArgAt === "number") {
+            throw args[this.throwArgAt];
         } else if (this.fakeFn) {
             return this.fakeFn.apply(context, args);
         } else if (this.resolve) {

diff --git a/lib/sinon/default-behaviors.js b/lib/sinon/default-behaviors.js
@@ -128,6 +128,14 @@ module.exports = {
         fake.returnArgAt = pos;
     },
 
+    throwsArg: function throwsArg(fake, pos) {
+        if (typeof pos !== "number") {
+            throw new TypeError("argument index is not number");
+        }
+
+        fake.throwArgAt = pos;
+    },
+
     returnsThis: function returnsThis(fake) {
         fake.returnThis = true;
     },

diff --git a/lib/sinon/stub.js b/lib/sinon/stub.js
@@ -92,6 +92,7 @@ var proto = {
 
         delete this.returnValue;
         delete this.returnArgAt;
+        delete this.throwArgAt;
         delete this.fakeFn;
         this.returnThis = false;
 

diff --git a/test/stub-test.js b/test/stub-test.js
@@ -279,6 +279,34 @@ describe("stub", function () {
         });
     });
 
+    describe(".throwsArg", function () {
+        it("throws argument at specified index", function () {
+            var stub = createStub.create();
+            stub.throwsArg(0);
+            var expectedError = new Error("The expected error message");
+
+            assert.exception(function () {
+                stub(expectedError);
+            }, function (err) {
+                return err.message === expectedError.message;
+            });
+        });
+
+        it("returns stub", function () {
+            var stub = createStub.create();
+
+            assert.same(stub.throwsArg(0), stub);
+        });
+
+        it("throws TypeError if no index is specified", function () {
+            var stub = createStub.create();
+
+            assert.exception(function () {
+                stub.throwsArg();
+            }, "TypeError");
+        });
+    });
+
     describe(".returnsThis", function () {
         it("stub returns this", function () {
             var instance = {};