add test case for output to stdout

prettier/main_test.ts

@@ -203,5 +203,30 @@ incididunt ut labore et dolore magna aliqua.
  await run([...cmd, "--end-of-line", "crlf", "--write", file2]);
  assertEquals(await getSourceCode(file2), "console.log({ a: 1 });\r\n");
 
+ await clearTestdataChanges();
+});
+
+test(async function testPrettierPrintToStdout() {
+ await clearTestdataChanges();
+
+ const file0 = join(testdata, "0.ts");
+ const file1 = join(testdata, "formatted.ts");
+
+ const getSourceCode = async (f: string) =>
+ decoder.decode(await Deno.readFile(f));
+
+ const { stdout } = await run([...cmd, file0]);
+ // the source file will not change without `--write` flags
+ assertEquals(await getSourceCode(file0), "console.log (0)\n");
+ // the output will be formatted code
+ assertEquals(stdout, "console.log(0);\n");
+
+ const { stdout:formattedCode } = await run([...cmd, file1]);
+ // the source file will not change without `--write` flags
+ assertEquals(await getSourceCode(file1), "console.log(0);\n");
+ // the output will be empty string. because the formatted content is same with before
+ assertEquals(formattedCode, "");
+
+
  await clearTestdataChanges();
 });

prettier/testdata/formatted.ts

@@ -0,0 +1 @@
+console.log(0);