Adds test for button pseudo attribute

Ensures that we can select buttons via the style pseudo attribute.

Change-Id: I89e95cb1534f4779b7488b04c189c17f7dce1238
Signed-off-by: Lars Vogel <Lars.Vogel@vogella.com>
Reviewed-on: https://git.eclipse.org/r/c/platform/eclipse.platform.ui/+/184831
diff --git a/tests/org.eclipse.e4.ui.tests.css.swt/src/org/eclipse/e4/ui/tests/css/swt/ButtonTest.java b/tests/org.eclipse.e4.ui.tests.css.swt/src/org/eclipse/e4/ui/tests/css/swt/ButtonTest.java
index 6007be7..02f5663 100644
--- a/tests/org.eclipse.e4.ui.tests.css.swt/src/org/eclipse/e4/ui/tests/css/swt/ButtonTest.java
+++ b/tests/org.eclipse.e4.ui.tests.css.swt/src/org/eclipse/e4/ui/tests/css/swt/ButtonTest.java
@@ -16,6 +16,7 @@
 package org.eclipse.e4.ui.tests.css.swt;
 
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNotEquals;
 
 import org.eclipse.swt.SWT;
 import org.eclipse.swt.graphics.FontData;
@@ -154,4 +155,17 @@
 		assertEquals(SWT.RIGHT, buttonToTest.getAlignment());
 	}
 
+	@Test
+	public void ensurePseudoAttributeAllowsToSelectionPushButton() {
+		Button buttonToTest = createTestButton("Button[style~='SWT.CHECK'] { background-color: #FF0000; color: #0000FF }");
+
+		assertEquals(RED, buttonToTest.getBackground().getRGB());
+		assertEquals(BLUE, buttonToTest.getForeground().getRGB());
+
+		Button unStyledButton = createTestButton("Button[style~='SWT.PUSH'] { background-color: #FF0000; color: #0000FF }");
+
+		assertNotEquals(RED, unStyledButton.getBackground().getRGB());
+		assertNotEquals(BLUE, unStyledButton.getForeground().getRGB());
+
+	}
 }