Add test showing problematic behaviour

src/test/java/com/github/joschi/jadconfig/JadConfigTest.java

@@ -8,6 +8,7 @@
 import com.github.joschi.jadconfig.testbeans.FoobarConfigurationBean;
 import com.github.joschi.jadconfig.testbeans.InheritedBeanSubClass;
 import com.github.joschi.jadconfig.testbeans.InheritedBeanSubSubClass;
+import com.github.joschi.jadconfig.testbeans.InvalidDefaultValueValidatorBean;
 import com.github.joschi.jadconfig.testbeans.Multi1ConfigurationBean;
 import com.github.joschi.jadconfig.testbeans.Multi2ConfigurationBean;
 import com.github.joschi.jadconfig.testbeans.NonExistingParameterBean;
@@ -503,6 +504,16 @@ public void testProcessValidatedBean() throws RepositoryException, ValidationExc
         Assert.assertEquals(1234567890123L, configurationBean.getMyLong());
     }
 
+    @Test
+    public void testProcessValidatedBeanInvalidDefaultValue() {
+        InvalidDefaultValueValidatorBean configurationBean = new InvalidDefaultValueValidatorBean();
+        jadConfig = new JadConfig(repository, configurationBean);
+
+        // the default value is -1, validator expects only positive longs => validation exception
+        Assert.assertThrows(ValidationException.class, () -> jadConfig.process());
+    }
+
+
     @Test
     public void testProcessNullPropertiesDoNotOverwriteDefaultValues() throws RepositoryException, ValidationException {
         final SingleFieldBean bean = new SingleFieldBean();

src/test/java/com/github/joschi/jadconfig/testbeans/InvalidDefaultValueValidatorBean.java

@@ -0,0 +1,14 @@
+package com.github.joschi.jadconfig.testbeans;
+
+import com.github.joschi.jadconfig.Parameter;
+import com.github.joschi.jadconfig.validators.PositiveLongValidator;
+
+public class InvalidDefaultValueValidatorBean {
+
+    @Parameter(value = "test.positive.long", validator = PositiveLongValidator.class)
+    private long myPositiveLong = -1;
+
+    public long getMyPositiveLong() {
+        return myPositiveLong;
+    }
+}