[PROPOSAL] Add more tests to the library (#865)

* phpunit: use dedicate `Tests` namespace for tests

* tests: replace phpunit with orchestra/testbench

* phpunit: ignore result cache file

* phpunit: adapt test for newer version

* tests: add base testcase class with a helper to run/assert commands

* tests: add test for ide-helper:eloquent

* travis: add global default variables

* travis: disable xdebug, speeds up running tests

* travis: convert php versions to build matrix for environment vars

* travis: only run phpcs/phpunit when the env vars signal it

However phpcs only runs with one test combination from the matrix,
not necessary to execute it every time.

tests/TestCase.php

@@ -0,0 +1,36 @@
+<?php declare(strict_types=1);
+
+namespace Barryvdh\LaravelIdeHelper\Tests;
+
+use Illuminate\Console\Command;
+use Orchestra\Testbench\TestCase as BaseTestCase;
+use Symfony\Component\Console\Tester\CommandTester;
+
+abstract class TestCase extends BaseTestCase
+{
+    /**
+     * The `CommandTester` is directly returned, use methods like
+     * `->getDisplay()` or `->getStatusCode()` on it.
+     *
+     * @param Command $command
+     * @param array $arguments The command line arguments, array of key=>value
+     *   Examples:
+     *   - named  arguments: ['model' => 'Post']
+     *   - boolean flags: ['--all' => true]
+     *   - arguments with values: ['--arg' => 'value']
+     * @param array $interactiveInput Interactive responses to the command
+     *   I.e. anything the command `->ask()` or `->confirm()`, etc.
+     * @return CommandTester
+     */
+    protected function runCommand(Command $command, array $arguments = [], array $interactiveInput = []): CommandTester
+    {
+        $command->setLaravel($this->app);
+
+        $tester = new CommandTester($command);
+        $tester->setInputs($interactiveInput);
+
+        $tester->execute($arguments);
+
+        return $tester;
+    }
+}