Fixed issue #359

Extracted construction into setUp() method.

exercises/diamond/src/test/java/DiamondPrinterTest.java

 import org.junit.Ignore;
+import org.junit.Before;
 import org.junit.Test;
 
 import java.util.List;
 import static org.junit.Assert.assertThat;
 
 public final class DiamondPrinterTest {
-
+    private DiamondPrinter diamondPrinter;
+    
+    @Before
+    
+    public void setUp() {
+        diamondPrinter = new DiamondPrinter();
+    }
+        
     @Test
     public void testOneByOneDiamond() {
-        List<String> output = new DiamondPrinter().printToList('A');
+        List<String> output = diamondPrinter.printToList('A');
         assertThat(output, is(singletonList("A")));
     }
 
     @Ignore
     @Test
     public void testTwoByTwoDiamond() {
-        List<String> output = new DiamondPrinter().printToList('B');
+        List<String> output = diamondPrinter.printToList('B');
         assertThat(output, is(asList(" A ",
                                      "B B",
                                      " A ")));
     @Ignore
     @Test
     public void testThreeByThreeDiamond() {
-        List<String> output = new DiamondPrinter().printToList('C');
+        List<String> output = diamondPrinter.printToList('C');
         assertThat(output, is(asList("  A  ",
                                      " B B ",
                                      "C   C",
     @Ignore
     @Test
     public void testFiveByFiveDiamond() {
-        List<String> output = new DiamondPrinter().printToList('E');
+        List<String> output = diamondPrinter.printToList('E');
         assertThat(output, is(asList("    A    ",
                                      "   B B   ",
                                      "  C   C  ",