reorg: move js runtime tests to cli/js/tests/ (#4250)

All Deno runtime test files were moved to cli/js/tests/ directory.

It makes a clear distinction that cli/js/tests/ contains code
that is run under Deno runtime as opposed to code in cli/js/ which
is used to create bundle and snapshot with "deno_typescript".

cli/js/tests/dir_test.ts

@@ -0,0 +1,54 @@
+// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
+import { unitTest, assert, assertEquals } from "./test_util.ts";
+
+unitTest(function dirCwdNotNull(): void {
+  assert(Deno.cwd() != null);
+});
+
+unitTest({ perms: { write: true } }, function dirCwdChdirSuccess(): void {
+  const initialdir = Deno.cwd();
+  const path = Deno.makeTempDirSync();
+  Deno.chdir(path);
+  const current = Deno.cwd();
+  if (Deno.build.os === "mac") {
+    assertEquals(current, "/private" + path);
+  } else {
+    assertEquals(current, path);
+  }
+  Deno.chdir(initialdir);
+});
+
+unitTest({ perms: { write: true } }, function dirCwdError(): void {
+  // excluding windows since it throws resource busy, while removeSync
+  if (["linux", "mac"].includes(Deno.build.os)) {
+    const initialdir = Deno.cwd();
+    const path = Deno.makeTempDirSync();
+    Deno.chdir(path);
+    Deno.removeSync(path);
+    try {
+      Deno.cwd();
+      throw Error("current directory removed, should throw error");
+    } catch (err) {
+      if (err instanceof Deno.errors.NotFound) {
+        assert(err.name === "NotFound");
+      } else {
+        throw Error("raised different exception");
+      }
+    }
+    Deno.chdir(initialdir);
+  }
+});
+
+unitTest({ perms: { write: true } }, function dirChdirError(): void {
+  const path = Deno.makeTempDirSync() + "test";
+  try {
+    Deno.chdir(path);
+    throw Error("directory not available, should throw error");
+  } catch (err) {
+    if (err instanceof Deno.errors.NotFound) {
+      assert(err.name === "NotFound");
+    } else {
+      throw Error("raised different exception");
+    }
+  }
+});