namespace tensorflow {
namespace {

void ExpectHasSubstr(const string& s, const string& expected) {
  EXPECT_TRUE(absl::StrContains(s, expected))
      << "'" << s << "' does not contain '" << expected << "'";
}

void ExpectHasNoSubstr(const string& s, const string& expected) {
  EXPECT_FALSE(absl::StrContains(s, expected))
      << "'" << s << "' should not contain '" << expected << "'";
}

// WritableFile that simply concats into string.