add tests

lab2/zad2/app/src/test/java/pl/jacekpoz/AppTest.java

@@ -1,11 +0,0 @@
-package pl.jacekpoz;
-
-import org.junit.jupiter.api.Test;
-import static org.junit.jupiter.api.Assertions.*;
-
-class AppTest {
-    @Test void appHasAGreeting() {
-        App classUnderTest = new App();
-        assertNotNull(classUnderTest.getGreeting(), "app should have a greeting");
-    }
-}

lab2/zad2/app/src/test/java/pl/jacekpoz/GFTest.java

@@ -0,0 +1,61 @@
+package pl.jacekpoz;
+
+import org.junit.jupiter.api.Test;
+import static org.junit.jupiter.api.Assertions.*;
+
+class GFTest {
+    @Test
+    void additionWorks() {
+        GF a = new GF(5, 2);
+        GF b = new GF(5, 4);
+
+        assertEquals(new GF(5, 1), a.add(b));
+    }
+
+    @Test
+    void subtractionWorks() {
+        GF a = new GF(5, 2);
+        GF b = new GF(5, 4);
+
+        assertEquals(new GF(5, 3), a.subtract(b));
+    }
+
+    @Test
+    void multiplicationWorks() {
+        GF a = new GF(6, 2);
+        GF b = new GF(6, 4);
+
+        assertEquals(new GF(6, 2), a.multiply(b));
+    }
+
+    @Test
+    void divisionWorks() {
+        GF a = new GF(7, 2);
+        GF b = new GF(7, 4);
+
+        assertEquals(new GF(7, 4), a.divide(b));
+    }
+
+    @Test
+    void divisionByZeroFails() {
+        GF a = new GF(5, 2);
+        GF b = new GF(5, 0);
+
+        Throwable ex = assertThrows(IllegalArgumentException.class, () -> {
+            a.divide(b);
+        });
+
+        assertEquals("division by 0 is illegal", ex.getMessage());
+    }
+
+    @Test
+    void differentCharacteristicsFail() {
+        GF a = new GF(10, 5);
+        GF b = new GF(8, 5);
+
+        Throwable ex = assertThrows(IllegalArgumentException.class, () -> {
+            a.add(b);
+        });
+        assertEquals("both arguments must have the same characteristic", ex.getMessage());
+    }
+}