feat: move Expectations API out of external plugin

tests/Features/Expect/toBeWritableFile.php

@@ -0,0 +1,23 @@
+<?php
+
+use PHPUnit\Framework\ExpectationFailedException;
+
+beforeEach(function () {
+    touch($this->tempFile = sys_get_temp_dir() . '/fake.file');
+});
+
+afterEach(function () {
+    unlink($this->tempFile);
+});
+
+test('pass', function () {
+    expect($this->tempFile)->toBeWritableFile();
+});
+
+test('failures', function () {
+    expect('/random/path/whatever.file')->toBeWritableFile();
+})->throws(ExpectationFailedException::class);
+
+test('not failures', function () {
+    expect($this->tempFile)->not->toBeWritableFile();
+})->throws(ExpectationFailedException::class);