[wip] add tests

tests/Filter/FilterParserTest.php

@@ -0,0 +1,47 @@
+<?php
+
+namespace Filter;
+
+use PHPUnit\Framework\TestCase;
+use TypeError;
+
+/**
+ * @covers \Filter\FilterParser
+ */
+class FilterParserTest extends TestCase
+{
+    private FilterParser $parser;
+
+    protected function setUp(): void
+    {
+        $this->parser = new FilterParser();
+    }
+
+    public function testCreatesSpecificFilters(): void
+    {
+        self::assertContainsOnlyInstancesOf(SpecificFilter::class, [
+            $this->parser->parse('title=poo'),
+            $this->parser->parse('1='),
+            $this->parser->parse('filepath=some_thing_else'),
+        ]);
+
+        self::assertNotInstanceOf(SpecificFilter::class, $this->parser->parse('='));
+    }
+
+    public function testCreatesGenericFilters(): void
+    {
+        // Basically, anything that does not match the pattern .+=.*
+        self::assertContainsOnlyInstancesOf(GenericFilter::class, [
+            $this->parser->parse('scoobypoo'),
+            $this->parser->parse('324234'),
+            $this->parser->parse(324234),
+            $this->parser->parse('baz'),
+        ]);
+    }
+
+    public function testDoesNotTakeNull(): void
+    {
+        $this->expectException(TypeError::class);
+        $this->parser->parse(null);
+    }
+}