test: augment tests for SourceTextModule

Adds tests for a few error conditions. Also, adds tests to make sure
the dynamically generated url is correct.

Author: aeisenberg

test/parallel/test-vm-module-basic.js

@@ -50,3 +50,16 @@ const { SourceTextModule, createContext } = require('vm');
   await m.evaluate({ timeout: 500 })
     .then(() => assert(false), () => {});
 })();
+
+// Check the generated url for each module
+(async () => {
+  const context1 = createContext({ });
+  const context2 = createContext({ });
+
+  const m1 = new SourceTextModule('1', { context: context1 });
+  assert.strictEqual(m1.url, 'vm:module(0)');
+  const m2 = new SourceTextModule('2', { context: context1 });
+  assert.strictEqual(m2.url, 'vm:module(1)');
+  const m3 = new SourceTextModule('3', { context: context2 });
+  assert.strictEqual(m3.url, 'vm:module(0)');
+})();

test/parallel/test-vm-module-errors.js

@@ -43,7 +43,8 @@ async function checkArgType() {
   });
 
   for (const invalidOptions of [
-    0, 1, null, true, 'str', () => {}, { url: 0 }, Symbol.iterator
+    0, 1, null, true, 'str', () => {}, { url: 0 }, Symbol.iterator,
+    { context: null }, { context: 'hucairz' }, { context: {} }
   ]) {
     common.expectsError(() => {
       new SourceTextModule('', invalidOptions);
@@ -222,6 +223,17 @@ async function checkLinking() {
   });
 }
 
+common.expectsError(() => {
+  new SourceTextModule('', {
+    importModuleDynamically: 'hucairz'
+  });
+}, {
+  code: 'ERR_INVALID_ARG_TYPE',
+  type: TypeError,
+  message: 'The "options.importModuleDynamically"' +
+    ' property must be of type function. Received type string'
+});
+
 // Check the JavaScript engine deals with exceptions correctly
 async function checkExecution() {
   await (async () => {