diff --git a/src/main/java/pl/uj/io/cuteanimals/action/ability/Focus.java b/src/main/java/pl/uj/io/cuteanimals/action/ability/Focus.java
index 6263460..a900e11 100644
--- a/src/main/java/pl/uj/io/cuteanimals/action/ability/Focus.java
+++ b/src/main/java/pl/uj/io/cuteanimals/action/ability/Focus.java
@@ -39,7 +39,7 @@ public IResult attack() {
         player.getFightManager()
                 .getEnemy()
                 .getAttributes()
-                .addHealth(damageDone - additionalDamage);
+                .addHealth(-damageDone - additionalDamage);
         var mobHealthLeft = player.getFightManager().getEnemy().getAttributes().getHealth();
 
         if (mobHealthLeft <= 0) {
diff --git a/src/main/java/pl/uj/io/cuteanimals/model/fight/FightManager.java b/src/main/java/pl/uj/io/cuteanimals/model/fight/FightManager.java
index bfb5dd5..af7f5a6 100644
--- a/src/main/java/pl/uj/io/cuteanimals/model/fight/FightManager.java
+++ b/src/main/java/pl/uj/io/cuteanimals/model/fight/FightManager.java
@@ -55,13 +55,10 @@ public IResult endBattle() {
         var playerAttrs = (PlayerAttributes) player.getAttributes();
         var playerLevel = playerAttrs.getLevel();
         var enemyLevel = fightingWith.getAttributes().getLevel();
+        var expBonus = playerLevel < enemyLevel ? Math.abs(playerLevel - enemyLevel) / 2 : 0;
         var gainedExperience =
-                (int)
-                        Math.round(
-                                ((playerAttrs.getRequiredExperience() / 6.0)
-                                        * (playerLevel < enemyLevel
-                                                ? 0.5
-                                                : 1 + Math.abs(playerLevel - enemyLevel) * 0.5)));
+                playerAttrs.getRequiredExperience() / 6 / (playerLevel < enemyLevel ? 2 : 1)
+                        + expBonus;
 
         ((PlayerAttributes) player.getAttributes()).addExperience(gainedExperience);
         player.getFightManager().setState(new ExplorationState(player));
diff --git a/src/test/java/pl/uj/io/cuteanimals/action/ability/FocusTest.java b/src/test/java/pl/uj/io/cuteanimals/action/ability/FocusTest.java
new file mode 100644
index 0000000..483bd32
--- /dev/null
+++ b/src/test/java/pl/uj/io/cuteanimals/action/ability/FocusTest.java
@@ -0,0 +1,53 @@
+package pl.uj.io.cuteanimals.action.ability;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import pl.uj.io.cuteanimals.model.Monster;
+import pl.uj.io.cuteanimals.model.NPCAttributes;
+import pl.uj.io.cuteanimals.model.Player;
+import pl.uj.io.cuteanimals.model.PlayerAttributes;
+
+class FocusTest {
+    private Player player;
+    private Monster dummy;
+    private PlayerAttributes attrs;
+
+    @BeforeEach
+    void setUp() {
+        player = new Player();
+        attrs = (PlayerAttributes) player.getAttributes();
+        player.getAttributes().addLevel(4);
+
+        dummy = new Monster("dummy", new NPCAttributes(0, 1, 1, 0));
+        player.getFightManager().beginFight(dummy);
+        var focus = new Focus();
+        focus.execute(player);
+    }
+
+    @Test
+    void shouldDrain20Mana() {
+        var manaBefore = attrs.getMana();
+        player.getFightManager().attack();
+        assertThat(attrs.getMana()).isEqualTo(manaBefore - 20);
+    }
+
+    @Test
+    void atLeast20ManaNeeded() {
+        attrs.addMana(-200);
+        var result = (new Focus()).execute(player);
+        assertThat(result.getMessage())
+                .isEqualTo("* Not enough mana! You need at least 20 mana to use this ability.");
+    }
+
+    @Test
+    void attackShouldInflictAdditionalDamage() {
+        player.getFightManager().attack();
+        var playerAttack = player.getAttributes().getAttack();
+        var playerDamage = attrs.getDamage();
+        var expected = -(playerDamage + 2 * playerAttack);
+        // getDamage is randomized
+        assertThat(dummy.getAttributes().getHealth()).isBetween(expected - 1, expected);
+    }
+}
diff --git a/src/test/java/pl/uj/io/cuteanimals/model/fight/FightManagerTest.java b/src/test/java/pl/uj/io/cuteanimals/model/fight/FightManagerTest.java
new file mode 100644
index 0000000..4d05367
--- /dev/null
+++ b/src/test/java/pl/uj/io/cuteanimals/model/fight/FightManagerTest.java
@@ -0,0 +1,49 @@
+package pl.uj.io.cuteanimals.model.fight;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import pl.uj.io.cuteanimals.model.Monster;
+import pl.uj.io.cuteanimals.model.NPCAttributes;
+import pl.uj.io.cuteanimals.model.Player;
+import pl.uj.io.cuteanimals.model.PlayerAttributes;
+
+class FightManagerTest {
+    private Player player;
+    private PlayerAttributes attrs;
+
+    @BeforeEach
+    void setUp() {
+        player = new Player();
+        attrs = (PlayerAttributes) player.getAttributes();
+    }
+
+    @Test
+    void endBattleEqualLevelExperienceTest() {
+        var dummy = new Monster("dummy", new NPCAttributes(1, 1, 1, 1));
+
+        player.getFightManager().beginFight(dummy);
+        player.getFightManager().endBattle();
+        assertThat(attrs.getExperience() == 1);
+    }
+
+    @Test
+    void endBattleMonsterHigherLevelExperienceTest() {
+        var dummy = new Monster("dummy", new NPCAttributes(1, 1, 11, 1));
+
+        player.getFightManager().beginFight(dummy);
+        player.getFightManager().endBattle();
+        assertThat(attrs.getExperience() == 1 + 5);
+    }
+
+    @Test
+    void endBattleMonsterLowerLevelExperienceTest() {
+        player.getAttributes().addLevel(1);
+        var dummy = new Monster("dummy", new NPCAttributes(1, 1, 11, 1));
+
+        player.getFightManager().beginFight(dummy);
+        player.getFightManager().endBattle();
+        assertThat(attrs.getExperience() == 1);
+    }
+}