Add functions to get the current and dotcom instance

src/github.test.ts

@@ -1,7 +1,8 @@
 import test from "ava";
 
+import { ActionsEnvVars } from "./environment";
 import * as github from "./github";
-import { setupTests } from "./testing-utils";
+import { getTestEnv, setupTests } from "./testing-utils";
 
 setupTests(test);
 
@@ -67,3 +68,44 @@ test("parseGitHubUrl", (t) => {
     message: '"http:///::::433" is not a valid URL',
   });
 });
+
+test("getCurrentInstance throws if required env vars aren't set", (t) => {
+  t.throws(() => github.getCurrentInstance(getTestEnv()));
+  t.throws(() => {
+    const env = getTestEnv({
+      [ActionsEnvVars.GITHUB_SERVER_URL]: "https://localhost",
+    });
+    github.getCurrentInstance(env);
+  });
+  t.throws(() => {
+    const env = getTestEnv({
+      [ActionsEnvVars.GITHUB_API_URL]: "https://api.localhost",
+    });
+    github.getCurrentInstance(env);
+  });
+});
+
+test("getCurrentInstance constructs instance from environment", (t) => {
+  const url = "https://localhost";
+  const apiUrl = "https://api.localhost";
+
+  const env = getTestEnv({
+    [ActionsEnvVars.GITHUB_SERVER_URL]: url,
+    [ActionsEnvVars.GITHUB_API_URL]: apiUrl,
+  });
+  const instance = github.getCurrentInstance(env);
+
+  t.is(instance.url, url);
+  t.is(instance.apiURL, apiUrl);
+});
+
+test("getCurrentInstance constructs dotcom instance with dotcom env vars", (t) => {
+  const env = getTestEnv({
+    [ActionsEnvVars.GITHUB_SERVER_URL]: github.GITHUB_DOTCOM_URL,
+    [ActionsEnvVars.GITHUB_API_URL]: github.GITHUB_DOTCOM_API_URL,
+  });
+  const instance = github.getCurrentInstance(env);
+  const dotcomInstance = github.getDotcomInstance();
+
+  t.deepEqual(dotcomInstance, instance);
+});