Fix hardcoded extension name string (#3222)

* Get `testExtensionId` from `package.json`
* Fix `ERR_AMBIGUOUS_ARGUMENT`

That `assert.throws` block actually shouldn't have had a message there. I mean,
it could have a message, but it was pointless to have it be the message that the
assertion throws, as that's not the point of that argument (which is what that
error means).

https://github.com/nodejs/node/blob/master/doc/api/errors.md#err_ambiguous_argument

Author: andyleejordan

test/features/ExternalApi.test.ts

@@ -6,7 +6,9 @@ import * as vscode from "vscode";
 import { before, beforeEach, afterEach } from "mocha";
 import { IExternalPowerShellDetails, IPowerShellExtensionClient } from "../../src/features/ExternalApi";
 
-const testExtensionId = "ms-vscode.powershell-preview";
+// tslint:disable-next-line: no-var-requires
+const PackageJSON: any = require("../../../package.json");
+const testExtensionId = `${PackageJSON.publisher}.${PackageJSON.name}`;
 
 suite("ExternalApi feature - Registration API", () => {
     let powerShellExtensionClient: IPowerShellExtensionClient;
@@ -42,8 +44,7 @@ suite("ExternalApi feature - Registration API", () => {
     */
     test("API fails if not registered", async () => {
         assert.rejects(
-            async () => await powerShellExtensionClient.getPowerShellVersionDetails(""),
-            "UUID provided was invalid, make sure you ran the 'powershellExtensionClient.registerExternalExtension(extensionId)' method and pass in the UUID that it returns to subsequent methods.");
+            async () => await powerShellExtensionClient.getPowerShellVersionDetails(""))
     });
 
     test("It can't register the same extension twice", async () => {
@@ -82,7 +83,7 @@ suite("ExternalApi feature - Other APIs", () => {
     });
 
     beforeEach(() => {
-        sessionId = powerShellExtensionClient.registerExternalExtension("ms-vscode.powershell-preview");
+        sessionId = powerShellExtensionClient.registerExternalExtension(testExtensionId);
     });
 
     afterEach(() => {

test/runTests.ts

@@ -6,6 +6,10 @@ import * as path from "path";
 
 import { runTests } from "vscode-test";
 
+// tslint:disable-next-line: no-var-requires
+const PackageJSON: any = require("../../package.json");
+const testExtensionId = `${PackageJSON.publisher}.${PackageJSON.name}`;
+
 async function main() {
     try {
         // The folder containing the Extension Manifest package.json
@@ -22,7 +26,7 @@ async function main() {
             extensionTestsPath,
             launchArgs: [
                 "--disable-extensions",
-                "--enable-proposed-api", "ms-vscode.powershell-preview",
+                "--enable-proposed-api", testExtensionId,
                 "./test"
             ],
             version: "insiders"