diff --git a/tests/dlfcn_test.cpp b/tests/dlfcn_test.cpp
index 1fdecdb..b31d7e4 100644
--- a/tests/dlfcn_test.cpp
+++ b/tests/dlfcn_test.cpp
@@ -53,7 +53,7 @@
 TEST(dlfcn, dlopen_failure) {
   void* self = dlopen("/does/not/exist", RTLD_NOW);
   ASSERT_TRUE(self == NULL);
-#if __BIONIC__
+#if defined(__BIONIC__)
   ASSERT_STREQ("dlopen failed: library \"/does/not/exist\" not found", dlerror());
 #else
   ASSERT_STREQ("/does/not/exist: cannot open shared object file: No such file or directory", dlerror());
@@ -92,14 +92,14 @@
   // NULL handle.
   sym = dlsym(NULL, "test");
   ASSERT_TRUE(sym == NULL);
-#if __BIONIC__
+#if defined(__BIONIC__)
   ASSERT_SUBSTR("dlsym library handle is null", dlerror());
 #else
   ASSERT_SUBSTR("undefined symbol: test", dlerror()); // glibc isn't specific about the failure.
 #endif
 
   // NULL symbol name.
-#if __BIONIC__
+#if defined(__BIONIC__)
   // glibc marks this parameter non-null and SEGVs if you cheat.
   sym = dlsym(self, NULL);
   ASSERT_TRUE(sym == NULL);
@@ -206,7 +206,7 @@
   dlerror(); // Clear any pending errors.
   void* handle;
 
-#ifdef __GLIBC__
+#if defined(__GLIBC__)
   // glibc was smart enough not to define RTLD_NOW as 0, so it can detect missing flags.
   handle = dlopen(NULL, 0);
   ASSERT_TRUE(handle == NULL);
diff --git a/tests/fcntl_test.cpp b/tests/fcntl_test.cpp
index 725ac4a..fb6b07e 100644
--- a/tests/fcntl_test.cpp
+++ b/tests/fcntl_test.cpp
@@ -73,7 +73,7 @@
 TEST(fcntl, fallocate_EINVAL) {
   TemporaryFile tf;
 
-#if !defined(__GLIBC__)
+#if defined(__BIONIC__)
   errno = 0;
   ASSERT_EQ(-1, fallocate(tf.fd, 0, 0, -1));
   ASSERT_EQ(EINVAL, errno);
@@ -98,7 +98,7 @@
   ASSERT_EQ(0, fstat(tf.fd, &sb));
   ASSERT_EQ(0, sb.st_size);
 
-#if !defined(__GLIBC__)
+#if defined(__BIONIC__)
   ASSERT_EQ(0, fallocate(tf.fd, 0, 0, 1));
   ASSERT_EQ(0, fstat(tf.fd, &sb));
   ASSERT_EQ(1, sb.st_size);
diff --git a/tests/fortify_test.cpp b/tests/fortify_test.cpp
index e0d055e..873c71e 100644
--- a/tests/fortify_test.cpp
+++ b/tests/fortify_test.cpp
@@ -668,7 +668,7 @@
 }
 
 TEST(DEATHTEST, FD_ISSET_fortified) {
-#ifdef __BIONIC__ // glibc catches this at compile-time.
+#if defined(__BIONIC__) // glibc catches this at compile-time.
   ::testing::FLAGS_gtest_death_test_style = "threadsafe";
   fd_set set;
   memset(&set, 0, sizeof(set));
diff --git a/tests/locale_test.cpp b/tests/locale_test.cpp
index 347b5b1..7d063f9 100644
--- a/tests/locale_test.cpp
+++ b/tests/locale_test.cpp
@@ -58,7 +58,7 @@
   EXPECT_EQ(NULL, setlocale(13, NULL));
   EXPECT_EQ(EINVAL, errno);
 
-#if __BIONIC__
+#if defined(__BIONIC__)
   // The "" locale is implementation-defined. For bionic, it's the C locale.
   // glibc will give us something like "en_US.UTF-8", depending on the user's configuration.
   EXPECT_STREQ("C", setlocale(LC_ALL, ""));
diff --git a/tests/regex_test.cpp b/tests/regex_test.cpp
index 659d1db..d026221 100644
--- a/tests/regex_test.cpp
+++ b/tests/regex_test.cpp
@@ -28,7 +28,7 @@
 
   char buf[80];
   regerror(REG_NOMATCH, &re, buf, sizeof(buf));
-#if __BIONIC__
+#if defined(__BIONIC__)
   ASSERT_STREQ("regexec() failed to match", buf);
 #else
   ASSERT_STREQ("No match", buf);
diff --git a/tests/sched_test.cpp b/tests/sched_test.cpp
index 7c19962..caf4c65 100644
--- a/tests/sched_test.cpp
+++ b/tests/sched_test.cpp
@@ -21,7 +21,7 @@
 #include <sys/types.h>
 #include <sys/wait.h>
 
-#ifdef __BIONIC__
+#if defined(__BIONIC__)
 static int child_fn(void* i_ptr) {
   *reinterpret_cast<int*>(i_ptr) = 42;
   return 123;
diff --git a/tests/stdio_test.cpp b/tests/stdio_test.cpp
index 4725350..655ad3f 100644
--- a/tests/stdio_test.cpp
+++ b/tests/stdio_test.cpp
@@ -219,7 +219,7 @@
 }
 
 TEST(stdio, snprintf_n) {
-#if !defined(__GLIBC__)
+#if defined(__BIONIC__)
   // http://b/14492135
   char buf[32];
   int i = 1234;
@@ -460,7 +460,7 @@
 
   errno = 0;
   EXPECT_EQ(EOF, fwprintf(fp, L"hello"));
-#if !defined(__GLIBC__)
+#if defined(__BIONIC__)
   EXPECT_EQ(EBADF, errno);
 #endif
 
@@ -478,7 +478,7 @@
 
   errno = 0;
   EXPECT_EQ(WEOF, fputwc(L'x', fp));
-#if !defined(__GLIBC__)
+#if defined(__BIONIC__)
   EXPECT_EQ(EBADF, errno);
 #endif
 }
@@ -521,7 +521,7 @@
   ASSERT_EQ(mb_four_bytes, static_cast<wchar_t>(fgetwc(fp)));
   EXPECT_EQ(0, fgetpos(fp, &pos5));
 
-#ifdef __BIONIC__
+#if defined(__BIONIC__)
   // Bionic's fpos_t is just an alias for off_t. This is inherited from OpenBSD
   // upstream. Glibc differs by storing the mbstate_t inside its fpos_t. In
   // Bionic (and upstream OpenBSD) the mbstate_t is stored inside the FILE
@@ -586,9 +586,9 @@
   // Store the "inside multi byte" position.
   fpos_t pos_inside_mb;
   ASSERT_EQ(0, fgetpos(fp, &pos_inside_mb));
-  #ifdef __BIONIC__
-    ASSERT_EQ(offset_inside_mb, static_cast<off_t>(pos_inside_mb));
-  #endif
+#if defined(__BIONIC__)
+  ASSERT_EQ(offset_inside_mb, static_cast<off_t>(pos_inside_mb));
+#endif
 
   // Reading from within a byte should produce an error.
   ASSERT_EQ(WEOF, fgetwc(fp));
diff --git a/tests/stdlib_test.cpp b/tests/stdlib_test.cpp
index fc0f0e1..978a60f 100644
--- a/tests/stdlib_test.cpp
+++ b/tests/stdlib_test.cpp
@@ -42,7 +42,7 @@
   EXPECT_EQ(902267124, lrand48());
   EXPECT_EQ(132366131, lrand48());
 
-#if __BIONIC__
+#if defined(__BIONIC__)
   // On bionic, random(3) is equivalent to lrand48...
   srandom(0x01020304);
   EXPECT_EQ(1409163720, random());
diff --git a/tests/sys_resource_test.cpp b/tests/sys_resource_test.cpp
index bd974cb..d6d99a0 100644
--- a/tests/sys_resource_test.cpp
+++ b/tests/sys_resource_test.cpp
@@ -18,7 +18,7 @@
 
 #include <sys/resource.h>
 
-#if __GLIBC__
+#if defined(__GLIBC__)
 /* The host glibc we're currently building with doesn't have prlimit64 yet. */
 static int prlimit64(pid_t, int resource, const struct rlimit64* new_limit, struct rlimit64* old_limit) {
   if (new_limit != NULL) {
@@ -30,7 +30,7 @@
 #endif
 
 TEST(sys_resource, smoke) {
-#if __LP64__ || __GLIBC__
+#if defined(__LP64__) || defined(__GLIBC__)
   ASSERT_EQ(sizeof(rlimit), sizeof(rlimit64));
   ASSERT_EQ(8U, sizeof(rlim_t));
 #else
diff --git a/tests/unistd_test.cpp b/tests/unistd_test.cpp
index 2b51aad..ff05039 100644
--- a/tests/unistd_test.cpp
+++ b/tests/unistd_test.cpp
@@ -67,7 +67,7 @@
   ASSERT_EQ(reinterpret_cast<void*>(-1), sbrk(-(current_brk + 1)));
   ASSERT_EQ(ENOMEM, errno);
 
-#if !defined(__GLIBC__)
+#if defined(__BIONIC__)
   // The maximum negative value is an interesting special case that glibc gets wrong.
   ASSERT_EQ(reinterpret_cast<void*>(-1), sbrk(PTRDIFF_MIN));
   ASSERT_EQ(ENOMEM, errno);
diff --git a/tests/wchar_test.cpp b/tests/wchar_test.cpp
index 30d7bff..c8aec2d 100644
--- a/tests/wchar_test.cpp
+++ b/tests/wchar_test.cpp
@@ -288,7 +288,7 @@
   // 4-byte UTF-8.
   ASSERT_EQ(4U, mbrtowc(out, "\xf0\xa4\xad\xa2" "ef", 6, NULL));
   ASSERT_EQ(static_cast<wchar_t>(0x24b62), out[0]);
-#if __BIONIC__ // glibc allows this.
+#if defined(__BIONIC__) // glibc allows this.
   // Illegal 5-byte UTF-8.
   ASSERT_EQ(static_cast<size_t>(-1), mbrtowc(out, "\xf8\xa1\xa2\xa3\xa4" "f", 6, NULL));
   ASSERT_EQ(EILSEQ, errno);