Added unit tests for CategoryUtility

src/test/java/ntnu/idatt2016/v233/SmartMat/util/CategoryUtilTest.java

+package ntnu.idatt2016.v233.SmartMat.util;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+public class CategoryUtilTest {
+
+    @Test
+    void testDefineCategory() {
+        String name = "kjøtt";
+        String description = "Prime cut of beef";
+        assertEquals("meat, fish and chicken", CategoryUtil.defineCategory(name, description));
+
+        name = "brød";
+        description = "Whole wheat bread";
+        assertEquals("baked goods and grains", CategoryUtil.defineCategory(name, description));
+
+        name = "melk";
+        description = "Whole milk";
+        assertEquals("dairy and egg ", CategoryUtil.defineCategory(name, description));
+
+        name = "eple";
+        description = "Fresh green apple";
+        assertEquals("fruit and vegetables", CategoryUtil.defineCategory(name, description));
+
+        name = "Something";
+        description = "Unknown product";
+        assertEquals("other", CategoryUtil.defineCategory(name, description));
+    }
+
+    @Test
+    void testGetCategoryName() {
+        assertEquals("meat, fish and chicken", CategoryUtil.getCategoryName(1));
+        assertEquals("baked goods and grains", CategoryUtil.getCategoryName(2));
+        assertEquals("dairy and egg", CategoryUtil.getCategoryName(3));
+        assertEquals("other", CategoryUtil.getCategoryName(4));
+        assertEquals("fruit and vegetables", CategoryUtil.getCategoryName(5));
+
+        int invalidCategoryNumber = 99;
+        assertThrows(IllegalArgumentException.class, () -> CategoryUtil.getCategoryName(invalidCategoryNumber));
+    }
+}