Add test for packages in Java

Author: mperor

FirstSteps/src/test/java/pl/mperor/lab/java/lang/element/PackageTest.java

@@ -0,0 +1,27 @@
+package pl.mperor.lab.java.lang.element;
+
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+import java.util.Arrays;
+import java.util.stream.Collectors;
+
+public class PackageTest {
+
+    @Test
+    public void testPackage() {
+        Assertions.assertEquals("pl.mperor.lab.java.lang.element",
+                PackageTest.class.getPackageName(),
+                "Package is a box for classes");
+
+        Assertions.assertEquals("pl.mperor.lab.java.lang.element.PackageTest",
+                PackageTest.class.getName(),
+                "Package + class name => unique address");
+
+        Assertions.assertEquals("pl.mperor",
+                Arrays.stream("mperor.pl".split("\\."))
+                        .sorted((_, _) -> -1)
+                        .collect(Collectors.joining(".")),
+                "Packages use the reversed domain name");
+    }
+}