to begin with, to end with, to contain: Error out if passed a needle …

…of the empty string.
unexpectedjs · Jul 30, 2015 · ea08ef3 · ea08ef3
1 parent bdf7b0e
commit ea08ef3
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diff --git a/lib/assertions.js b/lib/assertions.js
@@ -267,6 +267,11 @@ module.exports = function (expect) {
     expect.addAssertion('string', '[not] to contain', function (expect, subject) {
         var flags = this.flags;
         var args = Array.prototype.slice.call(arguments, 2);
+        args.forEach(function (arg) {
+            if (String(arg) === '') {
+                throw new Error("The '" + this.testDescription + "' assertion does not support the empty string");
+            }
+        }, this);
         expect.withError(function () {
             args.forEach(function (arg) {
                 expect(subject.indexOf(arg) !== -1, '[not] to be truthy');
@@ -366,6 +371,9 @@ module.exports = function (expect) {
     expect.addAssertion('string', '[not] to begin with', function (expect, subject, value) {
         var flags = this.flags;
         var stringValue = String(value);
+        if (stringValue === '') {
+            throw new Error("The '" + this.testDescription + "' assertion does not support a prefix of the empty string");
+        }
         expect.withError(function () {
             expect(subject.substr(0, stringValue.length), '[not] to equal', stringValue);
         }, function (err) {
@@ -394,6 +402,9 @@ module.exports = function (expect) {
     expect.addAssertion('string', '[not] to end with', function (expect, subject, value) {
         var flags = this.flags;
         var stringValue = String(value);
+        if (stringValue === '') {
+            throw new Error("The '" + this.testDescription + "' assertion does not support a suffix of the empty string");
+        }
         expect.withError(function () {
             expect(subject.substr(-stringValue.length), '[not] to equal', stringValue);
         }, function (err) {

diff --git a/test/unexpected.spec.js b/test/unexpected.spec.js
@@ -1698,6 +1698,12 @@ describe('unexpected', function () {
     });
 
     describe('contain assertion', function () {
+        it('should throw an error when one of the arguments is the empty string', function () {
+            expect(function () {
+                expect('foo', 'to contain', 'bar', '');
+            }, 'to throw', "The 'to contain' assertion does not support the empty string");
+        });
+
         it('asserts indexOf for a string', function () {
             expect('hello world', 'to contain', 'world');
         });
@@ -1816,6 +1822,12 @@ describe('unexpected', function () {
     });
 
     describe('to begin with assertion', function () {
+        it('should throw an error when the expected prefix is the empty string', function () {
+            expect(function () {
+                expect('foo', 'to begin with', '');
+            }, 'to throw', "The 'to begin with' assertion does not support a prefix of the empty string");
+        });
+
         describe('without the "not" flag', function () {
             it('asserts equality with a string', function () {
                 expect('hello', 'to begin with', 'hello');
@@ -1912,6 +1924,12 @@ describe('unexpected', function () {
     });
 
     describe('to end with assertion', function () {
+        it('should throw an error when the expected suffix is the empty string', function () {
+            expect(function () {
+                expect('foo', 'to end with', '');
+            }, 'to throw', "The 'to end with' assertion does not support a suffix of the empty string");
+        });
+
         describe('without the "not" flag', function () {
             it('asserts equality with a string', function () {
                 expect('hello', 'to end with', 'hello');