diff --git a/makefile b/makefile
index 9d42ef3..5166f03 100644
--- a/makefile
+++ b/makefile
@@ -15,15 +15,17 @@ HEADERS = purr.h mmap_file.h
 OBJS = purr.o socket.o urls.o files.o comm.o formats.o encrypt.o mmap_file.o
 
 TEST = tests
-TOBJS = tests.o formats.o urls.o
+TOBJS = tests.o formats.o urls.o mmap_file.o
 
 all: $(FINAL)
 
 check: $(TEST)
 	./tests
 
-$(OBJS): $(HEADERS)
-$(OBJS): CFLAGS += $(WARN) $(INC)
+$(OBJS) $(TOBJS): $(HEADERS)
+$(OBJS) $(TOBJS): CFLAGS += $(WARN)
+encrypt.o: CFLAGS += $(INC)
+
 purr: $(OBJS) $(LIBS)
 tests: $(TOBJS) $(LIBS)
 
diff --git a/mmap_file.h b/mmap_file.h
index c725d76..16718cf 100644
--- a/mmap_file.h
+++ b/mmap_file.h
@@ -4,7 +4,7 @@
 #include <stdint.h>
 #include <sys/mman.h>
 
-#define RESET_MMAP(file) do{(file).offset = 0; (file).cursor = 0}while(0);
+#define RESET_MMAP(file) do{(file).offset = 0; (file).cursor = 0;}while(0);
 #define ERROR_MMAP(file) ((file).data == MAP_FAILED || (file).data == NULL)
 #define CLOSE_MMAP(file) do{if((file).data != MAP_FAILED && (file).data != NULL) munmap((file).data, (file).size);}while(0);
 
diff --git a/tests.c b/tests.c
index 3750620..ca5e494 100644
--- a/tests.c
+++ b/tests.c
@@ -1,8 +1,11 @@
 #include <stdio.h>
+#include <stdlib.h>
 #include <string.h>
 #include <assert.h>
+#include <sys/random.h>
 
 #include "purr.h"
+#include "mmap_file.h"
 
 static int compare_strings(const char *expected, const char *result, const char *function)
 {
@@ -81,5 +84,21 @@ int main()
         assert(err == 0);
     }
 
+    {
+        /* mmap_file.c */
+        int write_size = 1024 * 1024;
+        struct mmap_file f = {.size = 2 * write_size, .prot = PROT_MEM, .flags = MAP_MEM};
+        f.data = mmap(NULL, f.size, f.prot, f.flags, -1, 0);
+        assert(!ERROR_MMAP(f));
+        uint8_t *data = malloc(write_size);
+        getrandom(data, write_size, 0);
+        assert(data);
+        int written = write_into_mmap(&f, data, write_size);
+        assert(f.offset == written);
+        RESET_MMAP(f);
+        read_from_mmap(&f, write_size);
+        rv = compare_arrays(data, f.data, write_size, "{write_into,read_from}_mmap") ? 1 : rv;
+    }
+
     return rv;
 }