2 files changed, 56 insertions, 0 deletions
diff --git a/chapter12/src/test/java/com/seaofnodes/simple/Chapter11Test.java b/chapter12/src/test/java/com/seaofnodes/simple/Chapter11Test.java
index a8b09226..17df1e3b 100644
--- a/chapter12/src/test/java/com/seaofnodes/simple/Chapter11Test.java
+++ b/chapter12/src/test/java/com/seaofnodes/simple/Chapter11Test.java
@@ -1,5 +1,6 @@
 package com.seaofnodes.simple;
 
+
 import com.seaofnodes.simple.evaluator.Evaluator;
 import com.seaofnodes.simple.node.StopNode;
 import org.junit.Test;
@@ -8,6 +9,20 @@ import org.junit.Test;
 import static org.junit.Assert.assertEquals;
 
 public class Chapter11Test {
+    @Test public void testPrintingPreservesGraph() throws Exception {
+        var stop = new Parser("while(arg < 10) arg = arg + 1; return arg;").parse().iterate();
+        GlobalCodeMotion.buildCFG(stop);
+        var bfs = new IRPrinter.BFS(stop,99);
+        for( var n : bfs._bfs )
+            if( n instanceof com.seaofnodes.simple.node.CFGNode cfg ) cfg._idepth = 0;
+        new com.seaofnodes.simple.node.ConstantNode(com.seaofnodes.simple.type.TypeInteger.constant(123456));
+        com.seaofnodes.simple.node.PrintTestSupport.unchanged(stop, () -> {
+            String first = stop.p(99);
+            assertEquals(first,stop.p(99));
+            stop.toString();
+        });
+    }
+
 
     // A placeholder test used to rapidly rotate through fuzzer produced issues
     @Test
diff --git a/chapter12/src/test/java/com/seaofnodes/simple/node/PrintTestSupport.java b/chapter12/src/test/java/com/seaofnodes/simple/node/PrintTestSupport.java
new file mode 100644
index 00000000..01d471bf
--- /dev/null
+++ b/chapter12/src/test/java/com/seaofnodes/simple/node/PrintTestSupport.java
@@ -0,0 +1,41 @@
+package com.seaofnodes.simple.node;
+import java.util.*;
+import static org.junit.Assert.*;
+
+// Inspect raw fields: the regression must not itself use lazy accessors.
+public class PrintTestSupport {
+    public static void unchanged(Node root, Runnable print) throws Exception {
+        var hash = Node.class.getDeclaredField("_hash");
+        hash.setAccessible(true);
+        var nodes = new ArrayList<Node>();
+        var seen = new IdentityHashMap<Node,Boolean>();
+        nodes.add(root);
+        seen.put(root,true);
+        for( int i=0; i<nodes.size(); i++ ) {
+            Node n = nodes.get(i);
+            for( Node def : n._inputs )
+                if( def!=null && seen.put(def,true)==null ) nodes.add(def);
+            for( Node use : n._outputs )
+                if( use!=null && seen.put(use,true)==null ) nodes.add(use);
+        }
+        var ins = new IdentityHashMap<Node,Node[]>();
+        var outs = new IdentityHashMap<Node,Node[]>();
+        var hashes = new IdentityHashMap<Node,Integer>();
+        var depths = new IdentityHashMap<Node,Integer>();
+        for( Node n : nodes ) {
+            ins.put(n,n._inputs.toArray(new Node[0]));
+            outs.put(n,n._outputs.toArray(new Node[0]));
+            hashes.put(n,hash.getInt(n));
+            if( n instanceof CFGNode cfg ) depths.put(n,cfg._idepth);
+        }
+        print.run();
+        for( Node n : nodes ) {
+            assertEquals("hash of node "+n._nid,(int)hashes.get(n),hash.getInt(n));
+            if( n instanceof CFGNode cfg ) assertEquals("depth of node "+n._nid,(int)depths.get(n),cfg._idepth);
+            assertEquals(ins.get(n).length,n.nIns());
+            assertEquals(outs.get(n).length,n.nOuts());
+            for( int i=0; i<n.nIns(); i++ ) assertSame(ins.get(n)[i],n.in(i));
+            for( int i=0; i<n.nOuts(); i++ ) assertSame(outs.get(n)[i],n._outputs.get(i));
+        }
+    }
+}