Add a basic test for each of the three "cat" commands (#1945)

Contributes to #1803.
Followup to #1902.

* Move cat_no_hash.dart from lib to bin

Fixes #1927

* Add a basic test for each of the three "cat" commands

* Ensure that there are no errors when dcat or dcat1 are run

Author: chalin

examples/misc/lib/tutorial/cat_no_hash.dart examples/misc/bin/cat_no_hash.dart

@@ -0,0 +1,46 @@
+import 'dart:convert';
+import 'dart:io';
+
+import 'package:test/test.dart';
+
+import '../bin/cat_no_hash.dart' as cat_no_hash;
+
+void main() {
+  const pathToQuotes = 'test_data/quote.txt';
+
+  test('cat_no_hash', () {
+    final quotes = File(pathToQuotes);
+    expect(quotes.readAsStringSync(), contains('#'));
+
+    expect(
+        () => cat_no_hash.main([quotes.path]),
+        prints(
+          isNot(contains('#')),
+        ));
+  });
+
+  test('dcat', () async {
+    final procResult = await Process.run(
+        'dart', ['--enable-asserts', 'bin/dcat.dart', '-n', pathToQuotes]);
+    expect(
+        procResult.stdout,
+        allOf(
+          startsWith('1'), // Line number
+          contains('Dr. Seuss'),
+          endsWith('Nietzsche\n'),
+        ));
+  });
+
+  test('dcat1', () async {
+    const greeting = '¡Hola, Mundo!';
+    final process =
+        await Process.start('dart', ['--enable-asserts', 'bin/dcat1.dart']);
+    process.stdin.writeln(greeting);
+    final output = await process.stdout.transform(Utf8Decoder()).join('');
+    final errors = await process.stderr.transform(Utf8Decoder()).join('');
+
+    expect(await process.exitCode, 0);
+    expect(output, contains('You typed: $greeting'));
+    expect(errors, isEmpty);
+  });
+}

examples/misc/test/bin_test.dart

@@ -0,0 +1,5 @@
+Be yourself. Everyone else is taken. -Oscar Wilde
+Don't cry because it's over, smile because it happened. -Dr. Seuss
+You only live once, but if you do it right, once is enough. -Mae West
+# This is a comment line.
+That which does not kill us makes us stronger. -Nietzsche

examples/misc/test_data/quote.txt

@@ -357,7 +357,7 @@ It first converts the data from UTF8 and then runs it through
 a [LineSplitter.][LineSplitter]
 All lines are printed, except any that begin with a hashtag, `#`.
 
-<?code-excerpt "misc/lib/tutorial/cat_no_hash.dart"?>
+<?code-excerpt "misc/bin/cat_no_hash.dart"?>
 {% prettify dart %}
 import 'dart:convert';
 import 'dart:io';