Add a basic test for FixedBitSet.setBits

More to follow.

build.xml

@@ -157,6 +157,9 @@
           <test name="org.edumips64.CpuTests">
               <formatter type="plain" usefile="false"/>
           </test>
+          <test name="org.edumips64.core.FixedBitSetTest">
+              <formatter type="plain" usefile="false"/>
+          </test>
       </junit>
       <delete dir="${outputDir}" />
   </target>

test/org/edumips64/core/FixedBitSetTest.java

@@ -0,0 +1,19 @@
+package org.edumips64.core;
+
+import org.edumips64.utils.IrregularStringOfBitsException;
+import org.junit.Test;
+
+import static org.junit.Assert.*;
+
+/**
+ * Tests the methods of FixedBitSet. Since it is an abstract base class,
+ * the methods are tested through BitSet64.
+ */
+public class FixedBitSetTest {
+    private BitSet64 bitset = new BitSet64();
+
+    @Test(expected = IrregularStringOfBitsException.class)
+    public void testIrregularStringOfBits() throws Exception {
+        bitset.setBits("blah", 0);
+    }
+}