diff --git a/src/DateFormatter.php b/src/DateFormatter.php
index 24e9af0..c3dfc4b 100644
--- a/src/DateFormatter.php
+++ b/src/DateFormatter.php
@@ -1,4 +1,5 @@
-<?php declare(strict_types=1);
+<?php
+declare(strict_types=1);
 
 namespace IW\Workshop;
 
@@ -9,11 +10,16 @@ class DateFormatter
     /**
      * Get current part of the day
      *
+     * @param $dateTime
      * @return string
      */
-    public function getPartOfDay() : string
+    public function getPartOfDay($dateTime = null) : string
     {
-        $dateTime    = new DateTime();
+        // default param, v parametru nemuze byt volani fce
+        if (!isset($dateTime)) {
+            $dateTime    = new DateTime();
+        }
+
         $currentHour = $dateTime->format('G');
 
         if ($currentHour >= 0 && $currentHour < 6)
diff --git a/tests/CalculatorTest.php b/tests/CalculatorTest.php
new file mode 100644
index 0000000..c96ef8b
--- /dev/null
+++ b/tests/CalculatorTest.php
@@ -0,0 +1,38 @@
+<?php
+
+use PHPUnit\Framework\TestCase;
+use IW\Workshop\Calculator;
+
+class CalculatorTest extends TestCase
+{
+
+    public function testAdd(): void
+    {
+        $this->assertEquals(
+            3,
+            Calculator::add(1, 2)
+        );
+
+        // navic i zaporne hodnoty
+        $this->assertEquals(
+            -3,
+            Calculator::add(-1, -2)
+        );
+    }
+
+    public function testDivideException(): void
+    {
+        $this->expectException(InvalidArgumentException::class);
+
+        // zavolat metodu, ktera zpusobi exception
+        Calculator::divide(1, 0);
+    }
+
+    public function testDivideOne(): void
+    {
+        $this->assertEquals(
+            2,
+            Calculator::divide(4, 2)
+        );
+    }
+}
diff --git a/tests/DateFormatterTest.php b/tests/DateFormatterTest.php
new file mode 100644
index 0000000..bde1fb3
--- /dev/null
+++ b/tests/DateFormatterTest.php
@@ -0,0 +1,24 @@
+<?php
+
+use PHPUnit\Framework\TestCase;
+use IW\Workshop\DateFormatter;
+
+class DateFormatterTest extends TestCase
+{
+
+    public function testGetPartOfDay(): void
+    {
+        $this->assertEquals("Night", DateFormatter::getPartOfDay(new DateTime("2018-05-27 0:00:01")));
+        $this->assertEquals("Night", DateFormatter::getPartOfDay(new DateTime("2018-05-27 5:59:01")));
+
+        $this->assertEquals("Morning", DateFormatter::getPartOfDay(new DateTime("2018-05-27 6:00:01")));
+        $this->assertEquals("Morning", DateFormatter::getPartOfDay(new DateTime("2018-05-27 11:59:01")));
+
+        $this->assertEquals("Afternoon", DateFormatter::getPartOfDay(new DateTime("2018-05-27 12:00:01")));
+        $this->assertEquals("Afternoon", DateFormatter::getPartOfDay(new DateTime("2018-05-27 17:59:01")));
+
+        // evening je od 18 do 24h? OK.
+        $this->assertEquals("Evening", DateFormatter::getPartOfDay(new DateTime("2018-05-27 18:01:01")));
+        $this->assertEquals("Evening", DateFormatter::getPartOfDay(new DateTime("2018-05-27 23:59:01")));
+    }
+}
\ No newline at end of file
diff --git a/tests/PostServiceTest.php b/tests/PostServiceTest.php
new file mode 100644
index 0000000..dd5752a
--- /dev/null
+++ b/tests/PostServiceTest.php
@@ -0,0 +1,82 @@
+<?php
+
+use PHPUnit\Framework\TestCase;
+use IW\Workshop\Client\Curl;
+use IW\Workshop\PostService;
+
+class PostServiceTest extends TestCase
+{
+
+    /**
+     * Happy day test, kdy vse dopadne dobre.
+     * @throws ReflectionException
+     */
+    public function testCreatePostHappyDay():void
+    {
+        // udelam moc clienta
+        $client = $this->createMock(Curl::class);
+
+        // ID noveho vytvoreneho clanku
+        $post_data = json_encode(array("id" => 901));
+
+        // konfigurace klienta
+        $client->method('post')->willReturn(array(201, $post_data));   // ok a vratit ID clanku na 901
+
+        // vytvorit postService s Mock clientem
+        $postService = new PostService($client);
+
+        // test vysledku jednotlivych volani
+        $this->assertEquals(901, $postService->createPost(array("fdsaf", "fdafad")));
+    }
+
+
+    /**
+     * Testuji runtime exception z jineho kodu nez 201.
+     *
+     * @throws ReflectionException
+     */
+    public function testCreatePostRuntimeException():void
+    {
+        $this->expectException(RuntimeException::class);
+
+        // udelam moc clienta
+        $client = $this->createMock(Curl::class);
+
+        // ID noveho vytvoreneho clanku
+        $post_data = json_encode(array("id" => 901));
+
+        // konfigurace klienta
+        $client->method('post')->willReturn(array(404, $post_data));   // chyba - vratit cokoliv nez 201
+
+        // vytvorit postService s Mock clientem
+        $postService = new PostService($client);
+
+        // test vysledku jednotlivych volani
+        $postService->createPost(array("fdsaf", "fdafad"));
+    }
+
+
+    /**
+     * Prazdny vstup by nemel vadit.
+     *
+     * @throws ReflectionException
+     */
+    public function testCreatePostEmptyInput():void
+    {
+        // udelam moc clienta
+        $client = $this->createMock(Curl::class);
+
+        // ID noveho vytvoreneho clanku
+        $post_data = json_encode(array("id" => 901));
+
+        // konfigurace klienta
+        $client->method('post')->willReturn(array(201, $post_data));   // ok
+
+        // vytvorit postService s Mock clientem
+        $postService = new PostService($client);
+
+        // test vysledku jednotlivych volani
+        $this->assertEquals(901, $postService->createPost(array()));
+    }
+}
+