refactor(std/example): Inconsistencies in the example tests (#7684)

std/examples/xeval_test.ts

@@ -0,0 +1,71 @@
+// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
+import { xeval } from "./xeval.ts";
+import { StringReader } from "../io/readers.ts";
+import { decode, encode } from "../encoding/utf8.ts";
+import {
+  assertEquals,
+  assertStringContains,
+  assert,
+} from "../testing/asserts.ts";
+import { dirname, fromFileUrl } from "../path/mod.ts";
+
+const moduleDir = dirname(fromFileUrl(import.meta.url));
+
+Deno.test("xevalSuccess", async function (): Promise<void> {
+  const chunks: string[] = [];
+  await xeval(new StringReader("a\nb\nc"), ($): number => chunks.push($));
+  assertEquals(chunks, ["a", "b", "c"]);
+});
+
+Deno.test("xevalDelimiter", async function (): Promise<void> {
+  const chunks: string[] = [];
+  await xeval(
+    new StringReader("!MADMADAMADAM!"),
+    ($): number => chunks.push($),
+    {
+      delimiter: "MADAM",
+    },
+  );
+  assertEquals(chunks, ["!MAD", "ADAM!"]);
+});
+
+const xevalPath = "xeval.ts";
+
+Deno.test({
+  name: "xevalCliReplvar",
+  fn: async function (): Promise<void> {
+    const p = Deno.run({
+      cmd: [
+        Deno.execPath(),
+        "run",
+        xevalPath,
+        "--replvar=abc",
+        "console.log(abc)",
+      ],
+      cwd: moduleDir,
+      stdin: "piped",
+      stdout: "piped",
+      stderr: "null",
+    });
+    assert(p.stdin != null);
+    await p.stdin.write(encode("hello"));
+    p.stdin.close();
+    assertEquals(await p.status(), { code: 0, success: true });
+    assertEquals(decode(await p.output()).trimEnd(), "hello");
+    p.close();
+  },
+});
+
+Deno.test("xevalCliSyntaxError", async function (): Promise<void> {
+  const p = Deno.run({
+    cmd: [Deno.execPath(), "run", xevalPath, "("],
+    cwd: moduleDir,
+    stdin: "null",
+    stdout: "piped",
+    stderr: "piped",
+  });
+  assertEquals(await p.status(), { code: 1, success: false });
+  assertEquals(decode(await p.output()), "");
+  assertStringContains(decode(await p.stderrOutput()), "Uncaught SyntaxError");
+  p.close();
+});