Index: trunk/test/unit/org/openstreetmap/josm/data/validation/OsmValidatorTest.java
===================================================================
--- trunk/test/unit/org/openstreetmap/josm/data/validation/OsmValidatorTest.java	(revision 15456)
+++ trunk/test/unit/org/openstreetmap/josm/data/validation/OsmValidatorTest.java	(revision 15459)
@@ -2,4 +2,8 @@
 package org.openstreetmap.josm.data.validation;
 
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+import org.junit.Before;
 import org.junit.Rule;
 import org.junit.Test;
@@ -19,6 +23,14 @@
     @Rule
     @SuppressFBWarnings(value = "URF_UNREAD_PUBLIC_OR_PROTECTED_FIELD")
-    public JOSMTestRules test = new JOSMTestRules();
+    public JOSMTestRules test = new JOSMTestRules().projection();
 
+    /**
+     * Setup test.
+     * @throws Exception if an error occurs
+     */
+    @Before
+    public void setUp() throws Exception {
+        OsmValidator.clearIgnoredErrors();
+    }
     /**
      * Tests that {@code OsmValidator} satisfies utility class criterias.
@@ -29,3 +41,45 @@
         UtilityClassTestUtil.assertUtilityClassWellDefined(OsmValidator.class);
     }
+
+    /**
+     * Test that {@link OsmValidator#cleanupIgnoredErrors()} really removes entry with element IDs when group is ignored
+     */
+    @Test
+    public void testCleanupIgnoredErrors1() {
+        OsmValidator.addIgnoredError("1351:n_2449148994:w_236955234", "Way end node near other way");
+        OsmValidator.addIgnoredError("1351:n_6871910559:w_733713588", "Way end node near other way");
+        OsmValidator.addIgnoredError("1351");
+        OsmValidator.cleanupIgnoredErrors();
+        assertTrue(OsmValidator.hasIgnoredError("1351"));
+        assertFalse(OsmValidator.hasIgnoredError("1351:n_6871910559:w_733713588"));
+        assertFalse(OsmValidator.hasIgnoredError("1351:n_2449148994:w_236955234"));
+    }
+
+    /**
+     * Non-regression test for <a href="https://josm.openstreetmap.de/ticket/17837">Bug #17837</a>.
+     * {@link OsmValidator#cleanupIgnoredErrors()} must not remove entry 1201 when 120 is before it.
+     */
+    @Test
+    public void testCleanupIgnoredErrorsTicket17837() {
+        OsmValidator.addIgnoredError("120");
+        OsmValidator.addIgnoredError("3000");
+        OsmValidator.addIgnoredError("1201"); // starts with 120, but has different code
+        OsmValidator.cleanupIgnoredErrors();
+        assertTrue(OsmValidator.hasIgnoredError("1201"));
+    }
+
+    /**
+     * Non-regression test for <a href="https://josm.openstreetmap.de/ticket/18223">Bug #18223</a>.
+     * {@link OsmValidator#cleanupIgnoredErrors()} must not combine primitives.
+     */
+    @Test
+    public void testCleanupIgnoredErrorsTicket18223() {
+        OsmValidator.addIgnoredError("1351:n_2449148994:w_236955234", "Way end node near other way");
+        OsmValidator.addIgnoredError("1351:n_6871910559:w_733713588", "Way end node near other way");
+        OsmValidator.cleanupIgnoredErrors();
+        assertFalse(OsmValidator.hasIgnoredError("1351"));
+        assertTrue(OsmValidator.hasIgnoredError("1351:n_2449148994:w_236955234"));
+        assertTrue(OsmValidator.hasIgnoredError("1351:n_6871910559:w_733713588"));
+    }
+
 }