Implemented unit tests for Manager and added param checks

scm-core/src/main/java/sonia/scm/Manager.java

@@ -41,6 +41,8 @@ import java.io.IOException;
 import java.util.Collection;
 import java.util.Comparator;
 
+import static com.google.common.base.Preconditions.checkArgument;
+
 /**
  * Base interface for all manager classes.
  *
@@ -139,6 +141,9 @@ public interface Manager<T extends ModelObject, E extends Exception>
    *         empty page result is returned.
    */
   default PageResult<T> getPage(Comparator<T> comparator, int pageNumber, int pageSize) {
+    checkArgument(pageSize > 0, "pageSize must be at least 1");
+    checkArgument(pageNumber >= 0, "pageNumber must be non-negative");
+
     Collection<T> entities = getAll(comparator, pageNumber * pageSize, pageSize + 1);
     boolean hasMore = entities.size() > pageSize;
     return new PageResult<>(Util.createSubCollection(entities, 0, pageSize), hasMore);

scm-core/src/test/java/sonia/scm/ManagerTest.java

@@ -0,0 +1,112 @@
+package sonia.scm;
+
+import org.junit.Test;
+import org.mockito.Mock;
+
+import java.io.IOException;
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.Comparator;
+
+import static org.junit.Assert.*;
+
+public class ManagerTest {
+
+  private Manager manager = new Manager() {
+    @Override
+    public void refresh(ModelObject object) throws IOException {
+
+    }
+
+    @Override
+    public ModelObject get(String id) {
+      return null;
+    }
+
+    @Override
+    public Collection getAll() {
+      return null;
+    }
+
+    @Override
+    public Collection getAll(Comparator comparator) {
+      return null;
+    }
+
+    @Override
+    public Collection getAll(int start, int limit) {
+      return null;
+    }
+
+    @Override
+    public Collection getAll(Comparator comparator, int start, int limit) {
+      if (start == 0 && (limit == 3) || (limit == 5)) {
+        return Arrays.asList(1, 2, 3);
+      } else if (start == 0 && limit == 6) {
+        return Collections.emptyList();
+      } else {
+        return Arrays.asList(3);
+      }
+    }
+
+    @Override
+    public void create(TypedObject object) throws Exception, IOException {}
+
+    @Override
+    public void delete(TypedObject object) throws Exception, IOException {}
+
+    @Override
+    public void modify(TypedObject object) throws Exception, IOException {}
+
+    @Override
+    public void close() throws IOException {}
+
+    @Override
+    public void init(SCMContextProvider context) {}
+
+    @Override
+    public Long getLastModified() { return null; }
+  };
+
+  @Mock
+  private Comparator comparator;
+
+
+  @Test(expected = IllegalArgumentException.class)
+  public void validatesPageNumber() {
+    manager.getPage(comparator, -1, 5);
+  }
+
+  @Test(expected = IllegalArgumentException.class)
+  public void validatesPageSize() {
+    manager.getPage(comparator, 2, 0);
+  }
+
+  @Test
+  public void getsNoPage() {
+    PageResult singlePage = manager.getPage(comparator, 0, 5);
+    assertFalse(singlePage.hasMore());
+    assertEquals(0, singlePage.getEntities().size());
+  }
+
+  @Test
+  public void getsSinglePage() {
+
+    PageResult singlePage = manager.getPage(comparator, 0, 4);
+    assertFalse(singlePage.hasMore());
+    assertEquals(3, singlePage.getEntities().size() );
+  }
+
+  @Test
+  public void getsTwoPages() {
+
+    PageResult page1 = manager.getPage(comparator, 0, 2);
+    assertTrue(page1.hasMore());
+    assertEquals(2, page1.getEntities().size());
+
+    PageResult page2 = manager.getPage(comparator, 1, 2);
+    assertFalse(page2.hasMore());
+    assertEquals(1, page2.getEntities().size());
+  }
+}