diff --git a/tests/C0/ProcessRunnerTest.php b/tests/C0/ProcessRunnerTest.php
index 4966ff0..f8fc040 100644
--- a/tests/C0/ProcessRunnerTest.php
+++ b/tests/C0/ProcessRunnerTest.php
@@ -2,9 +2,36 @@
 
 namespace Tests\C0;
 
+use App\ProcessRunner;
 use PHPUnit\Framework\TestCase;
 
 class ProcessRunnerTest extends TestCase
 {
-    // TODO: write 2 tests to coverage 100% code
+    public function test_return_2_WHEN_pass_case_1_case_3()
+    {
+        $sut = new ProcessRunner;
+
+        $actualResult = $sut->run(12, 1);
+
+        $expectedResult = 2;
+        $this->assertEquals($expectedResult, $actualResult);
+        $this->assertTrue($sut->wasProcess1Called());
+        $this->assertTrue($sut->wasProcess3Called());
+        $this->assertFalse($sut->wasProcess2Called());
+        $this->assertFalse($sut->wasProcess4Called());
+    }
+
+    public function test_return_2_WHEN_pass_case_2_case_4()
+    {
+        $sut = new ProcessRunner;
+
+        $actualResult = $sut->run(1, 1);
+
+        $expectedResult = 2;
+        $this->assertEquals($expectedResult, $actualResult);
+        $this->assertTrue($sut->wasProcess2Called());
+        $this->assertTrue($sut->wasProcess4Called());
+        $this->assertFalse($sut->wasProcess1Called());
+        $this->assertFalse($sut->wasProcess3Called());
+    }
 }
diff --git a/tests/C0/UsernameValidationTest.php b/tests/C0/UsernameValidationTest.php
index d78a816..76b4a3c 100644
--- a/tests/C0/UsernameValidationTest.php
+++ b/tests/C0/UsernameValidationTest.php
@@ -2,9 +2,67 @@
 
 namespace Tests\C0;
 
+use App\UsernameValidation;
 use PHPUnit\Framework\TestCase;
 
 class UsernameValidationTest extends TestCase
 {
-    // TODO: write 6 tests to coverage 100% code
+    public function test_return_false_when_user_name_lt_min_length()
+    {
+        $sut = new UsernameValidation;
+
+        $actualResult = $sut->isValid('');
+
+        $this->assertFalse($actualResult);
+        $this->assertEquals('Minimum length is 1', $sut->getMessage());
+    }
+
+    public function test_return_false_when_user_name_gt_max_length()
+    {
+        $sut = new UsernameValidation;
+
+        $actualResult = $sut->isValid('012345678901234567890');
+
+        $this->assertFalse($actualResult);
+        $this->assertEquals('Maximum length is 20', $sut->getMessage());
+    }
+
+    public function test_return_false_when_user_name_not_allow_dash_begin_or_end()
+    {
+        $sut = new UsernameValidation;
+
+        $actualResult = $sut->isValid('-1234');
+
+        $this->assertFalse($actualResult);
+        $this->assertEquals('- cannot appear at begin or end of name', $sut->getMessage());
+    }
+
+    public function test_return_false_when_user_name_not_allow_double_dash()
+    {
+        $sut = new UsernameValidation;
+
+        $actualResult = $sut->isValid('1--2');
+
+        $this->assertFalse($actualResult);
+        $this->assertEquals('Only single - is allowed', $sut->getMessage());
+    }
+
+    public function test_return_false_when_user_name_not_allow_invalid_character()
+    {
+        $sut = new UsernameValidation;
+
+        $actualResult = $sut->isValid('@');
+
+        $this->assertFalse($actualResult);
+        $this->assertEquals('Invalid character. Use only letters, digits and -', $sut->getMessage());
+    }
+
+    public function test_return_true_when_user_name_valid()
+    {
+        $sut = new UsernameValidation;
+
+        $actualResult = $sut->isValid('lethibaongan');
+
+        $this->assertTrue($actualResult);
+    }
 }