test: improve [unit] testing

Update and refresh this old PR:
- plantuml/plantuml#277

Add on test dependencies:
- [x] [`io.github.glytching:junit-extensions`](https://github.com/glytching/junit-extensions)
- [x] [`Mockito`](https://github.com/mockito/mockito)
  - `org.mockito:mockito-core`
  - `org.mockito:mockito-junit-jupiter`

Add a first test on:
- `test/utils/LineLocationImplTest.java`

build.gradle.kts

@@ -28,9 +28,14 @@ java {
 
 dependencies {
 	compileOnly("org.apache.ant:ant:1.10.13")
+
+	testImplementation("io.github.glytching:junit-extensions:2.6.0")
 	testImplementation("org.assertj:assertj-core:3.24.2")
 	testImplementation("org.junit.jupiter:junit-jupiter:5.9.2")
+	testImplementation("org.mockito:mockito-core:4.+")
+	testImplementation("org.mockito:mockito-junit-jupiter:4.+")
 	testImplementation("org.scilab.forge:jlatexmath:1.0.7")
+
 	"pdfRuntimeOnly"("org.apache.xmlgraphics:fop:2.8")
 	"pdfRuntimeOnly"("org.apache.xmlgraphics:batik-all:1.16")
 }

test/net/sourceforge/plantuml/utils/LineLocationImplTest.java

@@ -0,0 +1,122 @@
+package net.sourceforge.plantuml.utils;
+
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertSame;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+import io.github.glytching.junit.extension.random.Random;
+import io.github.glytching.junit.extension.random.RandomBeansExtension;
+
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.junit.jupiter.api.extension.Extensions;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.ValueSource;
+
+import org.mockito.Mock;
+import org.mockito.junit.jupiter.MockitoExtension;
+
+@Extensions({
+    @ExtendWith(MockitoExtension.class),
+    @ExtendWith(RandomBeansExtension.class)
+})
+
+class LineLocationImplTest {
+    @Mock
+    private LineLocation parent;
+    @Mock
+    private LineLocation parent2;
+
+    @Random
+    private String desc;
+    @Random
+    private String desc2;
+
+    @Test
+    void ctorDestArgMustNotBeNull() {
+        assertDoesNotThrow(() -> new LineLocationImpl(desc, null));
+        assertThrows(NullPointerException.class, () -> new LineLocationImpl(null, null));
+    }
+
+    @Test
+    void initialPositionIsNegativeOne() {
+        LineLocation loc = new LineLocationImpl(desc, null);
+        assertEquals(-1, loc.getPosition());
+    }
+
+    @Test
+    void parentSameAsProvided() {
+        LineLocation loc = new LineLocationImpl(desc, parent);
+        assertSame(parent, loc.getParent());
+    }
+
+    @Test
+    void descriptionSameAsProvided() {
+        LineLocation loc = new LineLocationImpl(desc, parent);
+        assertEquals(desc, loc.getDescription());
+    }
+
+    @Test
+    void toStringIsAConcatenationofDescAndPosition() {
+        LineLocationImpl loc = new LineLocationImpl(desc, parent);
+        assertEquals(desc + " : -1", loc.toString());
+        assertEquals(desc + " : 0", loc.oneLineRead().toString());
+    }
+
+    @Test
+    void oneLineReadMovesToNextLine() {
+        LineLocationImpl loc = new LineLocationImpl(desc, parent);
+
+        for (int i = 1; i < 5; ++i) {
+            LineLocationImpl next = loc.oneLineRead();
+            assertEquals(desc, next.getDescription());
+            assertSame(parent, next.getParent());
+            assertEquals(-1 + i, next.getPosition());
+            loc = next;
+        }
+    }
+
+    @Test
+    void comparisonStandardLibraryAlwaysDifferent() {
+        LineLocationImpl loc1 = new LineLocationImpl(desc, parent);
+        LineLocationImpl loc2 = new LineLocationImpl("<" + desc2, parent);
+
+        assertEquals(1, loc1.compareTo(loc2));
+        assertEquals(-1, loc2.compareTo(loc1));
+    }
+
+    @ParameterizedTest
+    @ValueSource(strings = {"", "<"})
+    void comparisonDisregardsDescription(String prefix) {
+        LineLocationImpl loc1 = new LineLocationImpl(prefix + desc, parent);
+        LineLocationImpl loc2 = new LineLocationImpl(prefix + desc2, parent);
+
+        assertEquals(0, loc1.compareTo(loc2));
+        assertEquals(0, loc2.compareTo(loc1));
+    }
+
+    @ParameterizedTest
+    @ValueSource(strings = {"", "<"})
+    void comparisonDisregardsParent(String prefix) {
+        LineLocationImpl loc1 = new LineLocationImpl(prefix + desc, parent);
+        LineLocationImpl loc2 = new LineLocationImpl(prefix + desc, parent2);
+
+        assertEquals(0, loc1.compareTo(loc2));
+        assertEquals(0, loc2.compareTo(loc1));
+    }
+
+    @ParameterizedTest
+    @ValueSource(strings = {"", "<"})
+    void comparisonLooksAtPositionOnly(String prefix) {
+        LineLocationImpl loc1 = new LineLocationImpl(prefix + desc, parent);
+        LineLocationImpl loc2 = loc1.oneLineRead();
+        LineLocationImpl loc3 = loc2.oneLineRead();
+
+        assertEquals(-1, loc1.compareTo(loc2));
+        assertEquals(1, loc2.compareTo(loc1));
+
+        assertEquals(-2, loc1.compareTo(loc3));
+        assertEquals(2, loc3.compareTo(loc1));
+    }
+}