Add unit tests for pow's behavior with NaNs.

Bug: 11669804
Change-Id: Idfa6527640c8d0c2cf3e5343bf7afe013e237545
diff --git a/tests/math_test.cpp b/tests/math_test.cpp
index 458a146..4c21a99 100644
--- a/tests/math_test.cpp
+++ b/tests/math_test.cpp
@@ -485,14 +485,20 @@
 }
 
 TEST(math, pow) {
+  ASSERT_TRUE(isnan(pow(nan(""), 3.0)));
+  ASSERT_TRUE(isnan(pow(2.0, nan(""))));
   ASSERT_FLOAT_EQ(8.0, pow(2.0, 3.0));
 }
 
 TEST(math, powf) {
+  ASSERT_TRUE(isnanf(powf(nanf(""), 3.0f)));
+  ASSERT_TRUE(isnanf(powf(2.0f, nanf(""))));
   ASSERT_FLOAT_EQ(8.0f, powf(2.0f, 3.0f));
 }
 
 TEST(math, powl) {
+  ASSERT_TRUE(__isnanl(powl(nanl(""), 3.0)));
+  ASSERT_TRUE(__isnanl(powl(2.0, nanl(""))));
   ASSERT_FLOAT_EQ(8.0, powl(2.0, 3.0));
 }