Adding a compare function to be used in expected object template

README.md

@@ -39,7 +39,14 @@ expect(obj).to.containSubset({
 		}
 	}
 });
-//or with 'not'
+
+// or using a compare function
+expect(obj).containSubset({
+	a: (expectedValue) => expectedValue,
+	c: (expectedValue) => expectedValue === 'd'
+})
+
+// or with 'not'
 expect(obj).to.not.containSubset({
 	g: 'whatever'
 });

lib/chai-subset.js

@@ -71,6 +71,9 @@
 				if (typeof(eo) === 'object' && eo !== null && ao !== null) {
 					return compare(eo, ao);
 				}
+				if (typeof(eo) === 'function') {
+					return eo(ao);
+				}
 				return ao === eo;
 			});
 		}

test/unit/chai-subset.spec.js

@@ -126,6 +126,20 @@ describe('circular objects', function() {
 	});
 });
 
+describe('object with compare function', function() {
+	it('should pass when function returns true', function () {
+		expect({a: 5}).to.containSubset({a: a => a});
+	});
+
+	it('should fail when function returns false', function () {
+		expect({a: 5}).to.not.containSubset({a: a => !a});
+	});
+
+	it('should pass for function with no arguments', function () {
+		expect({a: 5}).to.containSubset({a: () => true});
+	});
+});
+
 describe('comparison of non objects', function () {
 	it('should fail if actual subset is null', function () {
 		expect(null).to.not.containSubset({a: 1});