Fix WorkbenchInventoryMock#setMatrix (#960)

src/main/java/be/seeseemelk/mockbukkit/inventory/WorkbenchInventoryMock.java

@@ -51,7 +51,8 @@ public void setResult(@Nullable ItemStack newResult)
 	@Override
 	public void setMatrix(@Nullable ItemStack @NotNull [] contents)
 	{
-		Preconditions.checkArgument(super.getSize() <= contents.length, "Invalid inventory size. Expected " + super.getSize() + " or less, got " + contents.length);
+		Preconditions.checkNotNull(contents);
+		Preconditions.checkArgument(contents.length <= super.getSize(), "Invalid inventory size. Expected " + super.getSize() + " or less, got " + contents.length);
 		super.setContents(contents);
 	}
 

src/test/java/be/seeseemelk/mockbukkit/inventory/WorkbenchInventoryMockTest.java

@@ -8,9 +8,11 @@
 import org.junit.jupiter.api.Test;
 
 import static org.junit.jupiter.api.Assertions.assertArrayEquals;
+import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertNotNull;
 import static org.junit.jupiter.api.Assertions.assertNull;
+import static org.junit.jupiter.api.Assertions.assertThrows;
 
 class WorkbenchInventoryMockTest
 {
@@ -61,6 +63,26 @@ void testSetMatrix()
 		assertArrayEquals(matrix, workbench.getMatrix());
 	}
 
+	@Test
+	void testSetMatrix_underMaxSize()
+	{
+		ItemStack[] matrix = new ItemStack[5];
+		matrix[4] = new ItemStack(Material.OAK_BOAT);
+		assertDoesNotThrow(() -> workbench.setMatrix(matrix));
+	}
+
+	@Test
+	void testSetMatrix_overMaxSize()
+	{
+		assertThrows(IllegalArgumentException.class, () -> workbench.setMatrix(new ItemStack[12]));
+	}
+
+	@Test
+	void testSetMatrix_null()
+	{
+		assertThrows(NullPointerException.class, () -> workbench.setMatrix(null));
+	}
+
 	@Test
 	void testSetMatrix_SetsItems()
 	{