pw_string: Add EXPECT calls for static analyzer

In addition to the existing static asserts, explicitly check the value
of test values using the EXPECT macros.

Change-Id: Ifad02d8058b1d7f60535cd8cf92c1d5bb5b2fa86
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/31972
Pigweed-Auto-Submit: Prashanth Swaminathan <prashanthsw@google.com>
Commit-Queue: Keir Mierle <keir@google.com>
Reviewed-by: Wyatt Hepler <hepler@google.com>
Reviewed-by: Keir Mierle <keir@google.com>
diff --git a/pw_string/string_builder_test.cc b/pw_string/string_builder_test.cc
index c3bc3b0..0b092ad 100644
--- a/pw_string/string_builder_test.cc
+++ b/pw_string/string_builder_test.cc
@@ -523,12 +523,16 @@
 
   [[maybe_unused]] auto normal = MakeString("");
   static_assert(normal.max_size() == decltype(MakeString(1))::max_size());
+  EXPECT_EQ(normal.max_size(), decltype(MakeString(1))::max_size());
 
   [[maybe_unused]] auto resized =
       MakeString("This string is reeeeeeeeeaaaaallly long!!!!!");
   static_assert(resized.max_size() > decltype(MakeString(1))::max_size());
   static_assert(resized.max_size() ==
                 sizeof("This string is reeeeeeeeeaaaaallly long!!!!!") - 1);
+  EXPECT_GT(resized.max_size(), decltype(MakeString(1))::max_size());
+  EXPECT_EQ(resized.max_size(),
+            sizeof("This string is reeeeeeeeeaaaaallly long!!!!!") - 1);
 }
 
 TEST(MakeString, StringLiteral_UsesLongerFixedSize) {