Fix expression_test IsArithmetic

Change-Id: I77b799655321df4d4ffb21d8289c0f2c519786d7

internal/ceres/expression_test.cc

diff --git a/internal/ceres/expression_test.cc b/internal/ceres/expression_test.cc
index 704a464..d020192 100644
--- a/internal/ceres/expression_test.cc
+++ b/internal/ceres/expression_test.cc
@@ -50,8 +50,8 @@
 
   auto graph = StopRecordingExpressions();
 
-  ASSERT_FALSE(graph.ExpressionForId(a.id).IsArithmeticExpression());
-  ASSERT_FALSE(graph.ExpressionForId(b.id).IsArithmeticExpression());
+  ASSERT_TRUE(graph.ExpressionForId(a.id).IsArithmeticExpression());
+  ASSERT_TRUE(graph.ExpressionForId(b.id).IsArithmeticExpression());
   ASSERT_TRUE(graph.ExpressionForId(c.id).IsArithmeticExpression());
   ASSERT_TRUE(graph.ExpressionForId(d.id).IsArithmeticExpression());
 }