tests: Add more cases to test filter combinations

tests/Lib/Model/Department.php

@@ -0,0 +1,32 @@
+<?php
+
+namespace ipl\Tests\Orm\Lib\Model;
+
+use ipl\Orm\Model;
+use ipl\Orm\Relations;
+
+class Department extends Model
+{
+    public function getTableName()
+    {
+        return 'department';
+    }
+
+    public function getKeyName()
+    {
+        return 'id';
+    }
+
+    public function getColumns()
+    {
+        return [
+            'name'
+        ];
+    }
+
+    public function createRelations(Relations $relations)
+    {
+        $relations->hasMany('employee', Employee::class)
+            ->setJoinType('LEFT');
+    }
+}

tests/Lib/Model/Employee.php

@@ -0,0 +1,36 @@
+<?php
+
+namespace ipl\Tests\Orm\Lib\Model;
+
+use ipl\Orm\Model;
+use ipl\Orm\Relations;
+
+class Employee extends Model
+{
+    public function getTableName()
+    {
+        return 'employee';
+    }
+
+    public function getKeyName()
+    {
+        return 'id';
+    }
+
+    public function getColumns()
+    {
+        return [
+            'name',
+            'role',
+            'department_id',
+            'office_id'
+        ];
+    }
+
+    public function createRelations(Relations $relations)
+    {
+        $relations->belongsTo('department', Department::class);
+        $relations->belongsTo('office', Office::class)
+            ->setJoinType('LEFT');
+    }
+}

tests/Lib/Model/Office.php

@@ -0,0 +1,31 @@
+<?php
+
+namespace ipl\Tests\Orm\Lib\Model;
+
+use ipl\Orm\Model;
+use ipl\Orm\Relations;
+
+class Office extends Model
+{
+    public function getTableName()
+    {
+        return 'office';
+    }
+
+    public function getKeyName()
+    {
+        return 'id';
+    }
+
+    public function getColumns()
+    {
+        return [
+            'city'
+        ];
+    }
+
+    public function createRelations(Relations $relations)
+    {
+        $relations->hasMany('employee', Employee::class);
+    }
+}