Tests: Move sprintf test from AK/ to LibC/

This test doesn't test AK::String, but LibC's sprintf instead, so it
does not belong in `Tests/AK`. This also means this test won't be ran on
Lagom using the host OS's printf implementation.

Fixes a deprecated declaration warning when compiling with macOS SDK 13.

1 files changed, 14 insertions, 0 deletions

diff --git a/Tests/LibC/TestStdio.cpp b/Tests/LibC/TestStdio.cpp
index 0c0b818d0e..b23176b8e6 100644
--- a/Tests/LibC/TestStdio.cpp
+++ b/Tests/LibC/TestStdio.cpp
@@ -40,3 +40,17 @@ TEST_CASE(flush_on_exit)
         EXPECT_EQ(strcmp(test_str, buf), 0);
     }
 }
+
+TEST_CASE(sprintf_sign)
+{
+    char buf1[128];
+    int ret1 = sprintf(buf1, "%+d", 12);
+    EXPECT_EQ(ret1, 3);
+
+    char buf2[128];
+    int ret2 = sprintf(buf2, "%+d", -12);
+    EXPECT_EQ(ret2, 3);
+
+    EXPECT_EQ(buf1, "+12"sv);
+    EXPECT_EQ(buf2, "-12"sv);
+}