diff --git a/CMakeLists.txt b/CMakeLists.txt
index 0f00889..0a6dd44 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -35,6 +35,7 @@ set(SOURCES
   # signal
   src/signal/signal.c
   # stdio
+  src/stdio/files.c
   src/stdio/printf.c
   # stdlib
   src/stdlib/arith.c
diff --git a/include/ft/all-tests.h b/include/ft/all-tests.h
index b21aee3..6011acf 100644
--- a/include/ft/all-tests.h
+++ b/include/ft/all-tests.h
@@ -27,6 +27,7 @@ extern ft_test ft_signal_signal;
 extern ft_test ft_stdio_printf_basics;
 extern ft_test ft_stdio_printf_formats;
 extern ft_test ft_stdio_printf_fp;
+extern ft_test ft_stdio_open;
 
 /* stdlib */
 extern ft_test ft_stdlib_arith;
diff --git a/src/main.c b/src/main.c
index d44188f..d5dd1a8 100644
--- a/src/main.c
+++ b/src/main.c
@@ -43,6 +43,7 @@ ft_list headers_libc[] = {
         &ft_stdio_printf_basics,
         &ft_stdio_printf_formats,
         &ft_stdio_printf_fp,
+        &ft_stdio_open,
         NULL,
     }},
     { _("stdlib.h", "<stdlib.h>"), (ft_test*[]){
diff --git a/src/stdio/files.c b/src/stdio/files.c
new file mode 100644
index 0000000..2efe4b9
--- /dev/null
+++ b/src/stdio/files.c
@@ -0,0 +1,71 @@
+#include <ft/test.h>
+#include <ft/all-tests.h>
+#include <ft/util.h>
+
+#include <gint/gint.h>
+
+#include <errno.h>
+#include <string.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+#include "util.h"
+
+static void _stdio_open_switch(ft_test *t)
+{
+	int fd, rc;
+	FILE *fp;
+
+	/* Create a basic file */
+	DO_E(fd, creat("ft_stdio.txt", 0755), t, "%d");
+	ft_assert(t, fd >= 0);
+	DO_E(rc, write(fd, "Hello, stdio!\n", 14), t, "%d");
+	ft_assert(t, rc == 14);
+	DO_E(rc, close(fd), t, "%d");
+	ft_assert(t, rc == 0);
+
+	/* Try to open it with <stdio.h> */
+	DO_E(fp, fopen("ft_stdio.txt", "r"), t, "%p");
+	ft_assert(t, fp != NULL);
+	ft_log_FILE(t, "", fp);
+
+	/* Change buffer settings a couple times */
+	DO_E(rc, setvbuf(fp, NULL, _IONBF, 0), t, "%d");
+	ft_assert(t, rc == 0);
+	ft_log_FILE(t, "", fp);
+	DO_E(rc, setvbuf(fp, NULL, _IOLBF, 1024), t, "%d");
+	ft_assert(t, rc == 0);
+	ft_log_FILE(t, "", fp);
+	DO_E(rc, setvbuf(fp, NULL, _IOFBF, BUFSIZ), t, "%d");
+	ft_assert(t, rc == 0);
+	ft_log_FILE(t, "", fp);
+
+	/* Reopen with different permissions */
+	DO_E(fp, freopen("ft_stdio.txt", "w+", fp), t, "%p");
+	ft_assert(t, fp != NULL);
+	ft_log_FILE(t, "", fp);
+	DO_E(fp, freopen("ft_stdio.txt", "rb+", fp), t, "%p");
+	ft_assert(t, fp != NULL);
+	ft_log_FILE(t, "", fp);
+	DO_E(fp, freopen("ft_stdio.txt", "ab", fp), t, "%p");
+	ft_assert(t, fp != NULL);
+	ft_log_FILE(t, "", fp);
+	DO_E(fp, freopen("ft_stdio.txt", "w", fp), t, "%p");
+	ft_assert(t, fp != NULL);
+	ft_log_FILE(t, "", fp);
+
+	DO_E(rc, fclose(fp), t, "%d");
+	ft_assert(t, rc == 0);
+}
+
+static void _stdio_open(ft_test *t)
+{
+	gint_world_switch(GINT_CALL(_stdio_open_switch, (void *)t));
+}
+
+ft_test ft_stdio_open = {
+	.name = "Opening files",
+	.function = _stdio_open,
+};
diff --git a/src/stdio/util.h b/src/stdio/util.h
new file mode 100644
index 0000000..48d9b35
--- /dev/null
+++ b/src/stdio/util.h
@@ -0,0 +1,42 @@
+#ifndef _STDIO_UTIL_H
+#define _STDIO_UTIL_H
+
+#include <ft/test.h>
+#include <stdio.h>
+
+/* Print a FILE to an ft_test. */
+static inline void ft_log_FILE(ft_test *t, char const *prefix, FILE *fp)
+{
+    ft_log(t, "%s%s", prefix, (*prefix ? " " : ""));
+    if(!fp) {
+        ft_log(t, "(null)\n");
+        return;
+    }
+
+    ft_log(t, "{fd %d/%d, mode %s%s%s%s%s%s, %s",
+        fp->fd, fp->fdpos,
+        fp->readable ? "r" : "",
+        fp->writable ? "w" : "",
+        fp->append ? "A" : "",
+        fp->text ? "" : "b",
+        fp->error ? " ERROR" : "",
+        fp->eof ? " EOF" : "",
+        fp->bufmode == _IONBF ? "_IONBF" :
+        fp->bufmode == _IOLBF ? "_IOLBF" :
+        fp->bufmode == _IOFBF ? "_IOFBF" : "_???");
+
+    if(fp->bufmode != _IONBF) {
+        ft_log(t, " %p/%d", fp->buf, fp->bufsize);
+
+        if(fp->bufpos == 0)
+            ft_log(t, " EMPTY");
+        else if(fp->bufdir == __FILE_BUF_READ)
+            ft_log(t, " READ %d/%d", fp->bufpos, fp->bufread);
+        else if(fp->bufdir == __FILE_BUF_WRITE)
+            ft_log(t, " WRITE %d", fp->bufpos);
+    }
+
+    ft_log(t, "}\n");
+}
+
+#endif /* _STDIO_UTIL_H */