написал bit_count, тесты и добавил цель в Makefile

Makefile

@@ -1,7 +1,7 @@
 CFLAGS=-Wall -I munit -ggdb
 unittest_obj=munit/munit.o
 
-all: str_bin str_test
+all: str_bin str_test bit_test
 
 str_test: $(unittest_obj) str_lib.o str_test.o
 	$(CC) $(CFLAGS) -o $@ $^
@@ -9,8 +9,19 @@ str_test: $(unittest_obj) str_lib.o str_test.o
 str_bin: str_lib.o str_bin.o
 	$(CC) $(CFLAGS) -o $@ $^
 
-test: ./str_test
+bit_test: $(unittest_obj) bit_lib.o bit_test.o
+	$(CC) $(CFLAGS) -o $@ $^
+
+bit_lib.o: bit_lib.c bit_lib.h
+str_lib.o: str_lib.c str_lib.h
+str_bin.o: str_bin.c
+bit_test.o: bit_test.c bit_lib.h
+
+all: str_bin str_test bit_test
+
+test: all 
 	./str_test
+	./bit_test
 
 clean:
-	rm *_bin *.o $(unittest_obj) str_test
+	rm -f *_bin *.o $(unittest_obj) str_test bit_test

bit_lib.c

@@ -0,0 +1,10 @@
+#include "bit_lib.h"
+
+int bit_count(unsigned int number) {
+    int count = 0;
+    while (number) {
+        count += number & 1;   // если младший бит = 1 → +1
+        number >>= 1;          // сдвиг вправо
+    }
+    return count;
+}

bit_lib.h

@@ -0,0 +1,6 @@
+#ifndef BIT_LIB_H
+#define BIT_LIB_H
+
+int bit_count(unsigned int number);
+
+#endif

bit_test.c

@@ -0,0 +1,30 @@
+#include "munit.h"
+#include "bit_lib.h"
+
+static MunitResult
+test_bit_count_basic(const MunitParameter params[], void *data) {
+    (void) params; (void) data;
+
+    munit_assert_int(bit_count(0), ==, 0);          // 0b0
+    munit_assert_int(bit_count(1), ==, 1);          // 0b1
+    munit_assert_int(bit_count(2), ==, 1);          // 0b10
+    munit_assert_int(bit_count(3), ==, 2);          // 0b11
+    munit_assert_int(bit_count(15), ==, 4);         // 0b1111
+    munit_assert_int(bit_count(16), ==, 1);         // 0b10000
+    munit_assert_int(bit_count(255), ==, 8);        // 0b11111111
+
+    return MUNIT_OK;
+}
+
+static const MunitTest tests[] = {
+    { "/bit_count/basic", test_bit_count_basic, NULL, NULL, MUNIT_TEST_OPTION_NONE, NULL },
+    { NULL, NULL, NULL, NULL, MUNIT_TEST_OPTION_NONE, NULL }
+};
+
+static const MunitSuite suite = {
+   NULL, tests, NULL, 1, MUNIT_SUITE_OPTION_NONE
+};
+
+int main(int argc, const char *argv[]) {
+    return munit_suite_main(&suite, (void*) "", argc, (char * const*) argv);
+}