fixup test cases

Author: s1na

eth/tracers/js/tracer_test.go

@@ -102,13 +102,16 @@ func TestTracer(t *testing.T) {
 	}{
 		{ // tests that we don't panic on bad arguments to memory access
 			code: "{depths: [], step: function(log) { this.depths.push(log.memory.slice(-1,-2)); }, fault: function() {}, result: function() { return this.depths; }}",
-			want: `[{},{},{}]`,
+			want: ``,
+			fail: "Tracer accessed out of bound memory: offset -1, end -2 at step (<eval>:1:53(15))    in server-side tracer function 'step'",
 		}, { // tests that we don't panic on bad arguments to stack peeks
 			code: "{depths: [], step: function(log) { this.depths.push(log.stack.peek(-1)); }, fault: function() {}, result: function() { return this.depths; }}",
-			want: `["0","0","0"]`,
+			want: ``,
+			fail: "Tracer accessed out of bound stack: size 0, index -1 at step (<eval>:1:53(13))    in server-side tracer function 'step'",
 		}, { //  tests that we don't panic on bad arguments to memory getUint
 			code: "{ depths: [], step: function(log, db) { this.depths.push(log.memory.getUint(-64));}, fault: function() {}, result: function() { return this.depths; }}",
-			want: `["0","0","0"]`,
+			want: ``,
+			fail: "Tracer accessed out of bound memory: available 0, offset -64, size 32 at step (<eval>:1:58(13))    in server-side tracer function 'step'",
 		}, { // tests some general counting
 			code: "{count: 0, step: function() { this.count += 1; }, fault: function() {}, result: function() { return this.count; }}",
 			want: `3`,