diff --git a/.gitignore b/.gitignore
index 9a1cf70..05471f5 100644
--- a/.gitignore
+++ b/.gitignore
@@ -2,3 +2,5 @@
 /config/2-conditionals.mk
 /polytreewm
 /src/*.o
+/tests/*.o
+/tests/*.test
diff --git a/Makefile b/Makefile
index d5e560b..006e01d 100644
--- a/Makefile
+++ b/Makefile
@@ -22,6 +22,7 @@ MODULES_SRC = \
 	src/geom.c \
 	src/helpers.c \
 	src/layouts.c \
+	src/logger.c \
 	src/settings.c \
 	src/spawn.c \
 	src/state.c \
@@ -34,25 +35,37 @@ DWM_SRC = \
 	src/dwm/layouts.c \
 	src/dwm/xerror.c
 
+TEST_SRC = \
+	tests/geom_position.c \
+	tests/geom_sizes.c
+
+MAIN_SRC = $(MODULES_SRC) src/main.c
+
 MODULES_HDR = $(MODULES_SRC:.c=.h)
-DWM_HDR = $(DWM_SRC:.c=.h)
+DWM_HDR     = $(DWM_SRC:.c=.h)
+MAIN_HDR    = $(MODULES_HDR) src/main.h src/config.def.h
 
-SRC = $(MODULES_SRC) src/main.c
-HDR = $(MODULES_HDR) src/main.h src/config.def.h
+MODULES_OBJ = $(MODULES_SRC:.c=.o)
+TEST_OBJ    = $(TEST_SRC:.c=.o) tests/main.o
+MAIN_OBJ    = src/main.o
+ALL_OBJ     = $(MODULES_OBJ) $(TEST_OBJ) $(MAIN_OBJ)
 
-OBJ = $(SRC:.c=.o)
+TEST_EXE = $(TEST_SRC:.c=.test)
+ALL_EXE  = polytreewm $(TEST_EXE)
 
-polytreewm: $(OBJ)
-	$(CC) -o $@ $(OBJ) $(LDFLAGS)
+polytreewm: $(MAIN_OBJ) $(MODULES_OBJ)
+	$(CC) -o $@ $^ $(LDFLAGS)
 
-%.o: %.c
+%.o: %.c $(CONFIGMKS) $(HDR)
 	$(CC) -c $< -o $@ $(CFLAGS)
 
+%.test: %.o $(MODULES_OBJ) tests/main.o
+	$(CC) -o $@ $^ $(LDFLAGS)
+
 dwm.o: $(DWM_SRC) $(DWM_HDR)
-$(OBJ): $(CONFIGMKS) $(HDR)
 
 clean:
-	rm -f polytreewm $(OBJ)
+	rm -f $(ALL_OBJ) $(ALL_EXE)
 
 distclean: clean
 	rm -f $(CONFIGMKS_TO_REMOVE)
@@ -71,4 +84,7 @@ uninstall:
 		$(DESTDIR)$(BINDIR)/polytreewm \
 		$(DESTDIR)$(MANDIR)/man1/polytreewm.1
 
-.PHONY: all clean distclean install uninstall
+test: $(TEST_EXE)
+	@echo "$(TEST_EXE)" | awk '{ OFS="\n"; $$1=$$1 } 1' | sh
+
+.PHONY: all clean distclean install uninstall test
diff --git a/src/drw.c b/src/drw.c
index 8c84f76..f8aaa1c 100644
--- a/src/drw.c
+++ b/src/drw.c
@@ -1,4 +1,4 @@
-#include "main.h"
+#include "logger.h"
 #include "util.h"
 
 #include <stdio.h>
diff --git a/src/dwm.c b/src/dwm.c
index 021099c..f0bd6d7 100644
--- a/src/dwm.c
+++ b/src/dwm.c
@@ -2,6 +2,7 @@
 
 #include "helpers.h"
 #include "layouts.h"
+#include "logger.h"
 #include "main.h"
 #include "settings.h"
 #include "spawn.h"
diff --git a/src/logger.c b/src/logger.c
new file mode 100644
index 0000000..d311a2c
--- /dev/null
+++ b/src/logger.c
@@ -0,0 +1,93 @@
+#include "logger.h"
+
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+static void logger(const char *level, const char *fmt, ...);
+static void logger_perror(const char *level, const char *fmt, ...);
+
+void logger(const char *const level, const char *const fmt, ...)
+{
+	fprintf(stderr, PROGRAM_NAME": %s: ", level);
+
+	va_list ap;
+	va_start(ap, fmt);
+	vfprintf(stderr, fmt, ap);
+	va_end(ap);
+
+	fputc('\n', stderr);
+}
+
+void logger_perror(const char *const level, const char *const fmt, ...)
+{
+	fprintf(stderr, PROGRAM_NAME": %s: ", level);
+
+	va_list ap;
+	va_start(ap, fmt);
+	vfprintf(stderr, fmt, ap);
+	va_end(ap);
+
+	fprintf(stderr, ": ");
+	perror(NULL);
+}
+
+void fatal(const char *const fmt, ...)
+{
+	va_list ap;
+	va_start(ap, fmt);
+	logger("ERROR", fmt, ap);
+	va_end(ap);
+
+	exit(EXIT_FAILURE);
+}
+
+void fatal_perror(const char* const fmt, ...)
+{
+	va_list ap;
+	va_start(ap, fmt);
+	logger_perror("ERROR", fmt, ap);
+	va_end(ap);
+
+	exit(EXIT_FAILURE);
+}
+
+void fatal_nodie(const char *const fmt, ...)
+{
+	va_list ap;
+	va_start(ap, fmt);
+	logger("ERROR", fmt, ap);
+	va_end(ap);
+}
+
+void fatal_perror_nodie(const char *const fmt, ...)
+{
+	va_list ap;
+	va_start(ap, fmt);
+	logger_perror("ERROR", fmt, ap);
+	va_end(ap);
+}
+
+void warning(const char *const fmt, ...)
+{
+	va_list ap;
+	va_start(ap, fmt);
+	logger("WARN", fmt, ap);
+	va_end(ap);
+}
+
+void warning_perror(const char *const fmt, ...)
+{
+	va_list ap;
+	va_start(ap, fmt);
+	logger_perror("WARN", fmt, ap);
+	va_end(ap);
+}
+
+void info(const char *const fmt, ...)
+{
+	va_list ap;
+	va_start(ap, fmt);
+	logger("INFO", fmt, ap);
+	va_end(ap);
+}
diff --git a/src/logger.h b/src/logger.h
new file mode 100644
index 0000000..bc4b3df
--- /dev/null
+++ b/src/logger.h
@@ -0,0 +1,17 @@
+#ifndef _LOGGER_H
+#define _LOGGER_H
+
+#define PROGRAM_TITLE "PolytreeWM"
+#define PROGRAM_NAME  "polytreewm"
+
+__attribute__((noreturn))
+void fatal(const char *fmt, ...);
+__attribute__((noreturn))
+void fatal_perror(const char *fmt, ...);
+void fatal_nodie(const char *fmt, ...);
+void fatal_perror_nodie(const char *fmt, ...);
+void warning(const char *fmt, ...);
+void warning_perror(const char *fmt, ...);
+void info(const char *fmt, ...);
+
+#endif // _LOGGER_H
diff --git a/src/main.c b/src/main.c
index df0be8d..0c54c1c 100644
--- a/src/main.c
+++ b/src/main.c
@@ -1,10 +1,10 @@
 #include "main.h"
 
 #include "dwm.h"
+#include "logger.h"
 
 #include <locale.h>
 #include <signal.h>
-#include <stdarg.h>
 #include <stddef.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -12,16 +12,10 @@
 #include <sys/wait.h>
 #include <unistd.h>
 
-#define PROGRAM_TITLE "PolytreeWM"
-#define PROGRAM_NAME  "polytreewm"
-
 static char *program_exe = NULL;
 
 static void signal_callback(int signo);
 
-static void logger(const char *level, const char *fmt, ...);
-static void logger_perror(const char *level, const char *fmt, ...);
-
 int main(int argc, char *argv[])
 {
 	if (argc == 2 &&
@@ -83,88 +77,3 @@ void restart()
 	execvp(program_exe, args);
 	fatal_perror("restart with `execvp' failed");
 }
-
-void logger(const char *const level, const char *const fmt, ...)
-{
-	fprintf(stderr, PROGRAM_NAME": %s: ", level);
-
-	va_list ap;
-	va_start(ap, fmt);
-	vfprintf(stderr, fmt, ap);
-	va_end(ap);
-
-	fputc('\n', stderr);
-}
-
-void logger_perror(const char *const level, const char *const fmt, ...)
-{
-	fprintf(stderr, PROGRAM_NAME": %s: ", level);
-
-	va_list ap;
-	va_start(ap, fmt);
-	vfprintf(stderr, fmt, ap);
-	va_end(ap);
-
-	fprintf(stderr, ": ");
-	perror(NULL);
-}
-
-void fatal(const char *const fmt, ...)
-{
-	va_list ap;
-	va_start(ap, fmt);
-	logger("ERROR", fmt, ap);
-	va_end(ap);
-
-	exit(EXIT_FAILURE);
-}
-
-void fatal_perror(const char* const fmt, ...)
-{
-	va_list ap;
-	va_start(ap, fmt);
-	logger_perror("ERROR", fmt, ap);
-	va_end(ap);
-
-	exit(EXIT_FAILURE);
-}
-
-void fatal_nodie(const char *const fmt, ...)
-{
-	va_list ap;
-	va_start(ap, fmt);
-	logger("ERROR", fmt, ap);
-	va_end(ap);
-}
-
-void fatal_perror_nodie(const char *const fmt, ...)
-{
-	va_list ap;
-	va_start(ap, fmt);
-	logger_perror("ERROR", fmt, ap);
-	va_end(ap);
-}
-
-void warning(const char *const fmt, ...)
-{
-	va_list ap;
-	va_start(ap, fmt);
-	logger("WARN", fmt, ap);
-	va_end(ap);
-}
-
-void warning_perror(const char *const fmt, ...)
-{
-	va_list ap;
-	va_start(ap, fmt);
-	logger_perror("WARN", fmt, ap);
-	va_end(ap);
-}
-
-void info(const char *const fmt, ...)
-{
-	va_list ap;
-	va_start(ap, fmt);
-	logger("INFO", fmt, ap);
-	va_end(ap);
-}
diff --git a/src/main.h b/src/main.h
index d24651d..1927eb1 100644
--- a/src/main.h
+++ b/src/main.h
@@ -1,16 +1,6 @@
 #ifndef _MAIN_H
 #define _MAIN_H
 
-__attribute__((noreturn))
-void fatal(const char *fmt, ...);
-__attribute__((noreturn))
-void fatal_perror(const char *fmt, ...);
-void fatal_nodie(const char *fmt, ...);
-void fatal_perror_nodie(const char *fmt, ...);
-void warning(const char *fmt, ...);
-void warning_perror(const char *fmt, ...);
-void info(const char *fmt, ...);
-
 __attribute__((noreturn))
 void restart();
 
diff --git a/src/util.c b/src/util.c
index b2dacb5..ab0548b 100644
--- a/src/util.c
+++ b/src/util.c
@@ -1,6 +1,6 @@
 #include "util.h"
 
-#include "main.h"
+#include "logger.h"
 
 #include <stdarg.h>
 #include <stdio.h>
diff --git a/src/xbase.c b/src/xbase.c
index d19af11..1f6a448 100644
--- a/src/xbase.c
+++ b/src/xbase.c
@@ -1,6 +1,6 @@
 #include "xbase.h"
 
-#include "main.h"
+#include "logger.h"
 
 #include <stdlib.h>
 #include <string.h>
diff --git a/tests/geom_position.c b/tests/geom_position.c
new file mode 100644
index 0000000..726c660
--- /dev/null
+++ b/tests/geom_position.c
@@ -0,0 +1,3 @@
+int test() {
+	return 0;
+}
diff --git a/tests/geom_sizes.c b/tests/geom_sizes.c
new file mode 100644
index 0000000..726c660
--- /dev/null
+++ b/tests/geom_sizes.c
@@ -0,0 +1,3 @@
+int test() {
+	return 0;
+}
diff --git a/tests/main.c b/tests/main.c
new file mode 100644
index 0000000..fc362c5
--- /dev/null
+++ b/tests/main.c
@@ -0,0 +1,19 @@
+#include <stdio.h>
+
+int test();
+
+void restart() {}
+
+int main(int argc, char **argv)
+{
+	const char *const test_name = argv[0];
+	const int test_result = test();
+
+	if (test_result == 0) {
+		printf("[ OK ] %s\n", test_name);
+	} else {
+		printf("[FAIL] %s\n", test_name);
+	}
+
+	return test_result;
+}