Add test cases for bad options in babel-preset-es2015 (#5720)

* Added testcases for bad 'spec' or 'module' option

* Corrected typo in test description

packages/babel-preset-es2015/test/index.js

@@ -18,6 +18,14 @@ describe("es2015 preset", function () {
       });
     });
 
+    describe("spec", function () {
+      it("throws on non-boolean value", function () {
+        expect(function () {
+          es2015(null, { spec: 1 });
+        }).to.throw(/must be a boolean/);
+      });
+    });
+
     describe("modules", function () {
       it("doesn't throw when passing one false", function () {
         expect(function () {
@@ -42,6 +50,12 @@ describe("es2015 preset", function () {
           es2015(null, { modules: "systemjs" });
         }).not.to.throw();
       });
+
+      it("throws when passing neither false nor one of: 'commonjs', 'amd', 'umd', 'systemjs'", function () {
+        expect(function () {
+          es2015(null, { modules: 1 });
+        }).to.throw();
+      });
     });
   });
 });