diff --git a/cig.h b/cig.h
index 097fefe..ee5cf68 100644
--- a/cig.h
+++ b/cig.h
@@ -15,10 +15,6 @@ typedef union any_align { char c; int i; long l; long long ll; float f; double d
 #define MB (KB * KB)
 #define GB (KB * KB * KB)
 #define PTR_FROM_FIELD_PTR(STRUCT, FIELD, PTR) ((STRUCT *) (((char *) PTR) - offsetof(STRUCT, FIELD)))
-#define TODO(...) do { \
-	fprintf(stderr, "%s:%d: TODO: %s", __FILE__, (int)__LINE__, #__VA_ARGS__);\
-	exit(1); \
-} while (0)
 
 // Contains all operations an allocator can do. Similar interface to sdtlibs
 // malloc, realloc and free.
@@ -239,11 +235,15 @@ void arr_qsort(void *this, dyn_array_cmp_fn cmp_fn);
 
 // maps ////////////////////////////////////////////////////////////////////
 
-typedef int (*hash_func_t)(void *key);
-typedef int (*equals_func_t)(void *key1, void *key2);
+typedef unsigned int (*hash_func_t)(void *key);
+typedef bool (*equals_func_t)(void *key1, void *key2);
 
 typedef struct map_header {
-	int n_items, capacity, itemsize, keysize, mapping_capacity;
+	int capacity;
+	int itemsize;
+	int keysize;
+	int mapping_capacity;
+	int n_items;
 	allocator_t allocator;
 	hash_func_t hash;
 	equals_func_t equals;
diff --git a/justfile b/justfile
new file mode 100644
index 0000000..ab443b5
--- /dev/null
+++ b/justfile
@@ -0,0 +1,22 @@
+CC := "zig cc"
+CFLAGS := "-pedantic -Wall -Wextra -Wno-override-init -O0 -g -fno-omit-frame-pointer -fno-inline"
+LDFLAGS := "-lcriterion"
+TESTBIN := "/tmp/all_tests"
+
+set shell := ["bash", "-cu"]
+
+test: build
+	{{TESTBIN}}
+
+test_memcheck: build
+	valgrind --leak-check=full \
+	          --show-leak-kinds=all \
+	          --trace-children=yes \
+	          --error-exitcode=1 \
+	          {{TESTBIN}}
+
+build:
+	find "$PWD" -type f -name 'test*.c' | xargs -r {{CC}} {{CFLAGS}} _allocator_impl.c -o {{TESTBIN}} {{LDFLAGS}}
+
+tags:
+	find "$PWD" -type f \( -name '*.c' -o -name '*.h' \) | xargs ctags
diff --git a/makefile b/makefile
index ce3db8c..05ed79e 100644
--- a/makefile
+++ b/makefile
@@ -30,9 +30,3 @@ CRITERION_HEADERS := $(shell find /usr/include/criterion)
 ALL_FILES := $(PROJECT_C_FILES) $(CRITERION_HEADERS)
 tags: $(ALL_FILES)
 	ctags -R $(ALL_FILES)
-
-scratch: /tmp/scratch
-	valgrind --leak-check=full --show-leak-kinds=all --error-exitcode=1 /tmp/scratch
-
-/tmp/scratch: scratch.c
-	gcc scratch.c -o /tmp/scratch
diff --git a/map.c b/map.c
index 83d4310..e426738 100644
--- a/map.c
+++ b/map.c
@@ -75,10 +75,13 @@ void *map_grow_func(void *this, const char *file, int line) {
 		);
 		header = allocator_resize_func(allocator, header, new_size.bytes, file, line);
 		
-		TODO(
-			Overwrite the mapping arr with -1, then iterate through the items
-			arr and find the hashes of the values to populate the mappings
-		);
+		static_assert(0, "Overwrite the mapping arr with -1, then iterate"
+		"through the items arr and find the hashes of the values to populate the"
+		"mappings");
+			
+		static_assert(0, "make sure the mapping_arr field is set to the new and"
+		"correct pointer!");
+			
 	}
 
 	header->n_items = new_size;
@@ -97,7 +100,30 @@ void map_shrink_func(void *this, const char *file, int line) {
 	}
 	map_header_t *header = PTR_FROM_FIELD_PTR(map_header_t, bytes, this);
 	header->n_items--;
-	TODO(Hash the key at the removed item to find it in the mapping array, and set it to the gravestone value.);
+	static_assert(0, "Hash the key at the removed item to find it in the mapping array, and set it to the gravestone value.");
+}
+
+static inline uint32_t fnv_1a(const uint8_t *bytes, const int length) {
+	// Yanked from: https://en.wikipedia.org/wiki/Fowler%E2%80%93Noll%E2%80%93Vo_hash_function
+	const uint32_t PRIME = 0x01000193;
+	const uint32_t OFFSET = 0x811c9dc5;
+	uint32_t hash = OFFSET;
+	for (int i = 0; i < length; i++) {
+		uint32_t byte = (uint32_t)bytes[i];
+		hash = hash ^ byte;
+		hash = hash * PRIME;
+	}
+	return hash;
+}
+
+unsigned int map_hash(void *this, void *value) {
+	map_header_t *header = PTR_FROM_FIELD_PTR(map_header_t, bytes, this);
+	if (header->hash) {
+		static_assert(0, "hash using the hasing function");
+		return;
+	}
+	static_assert(0, "WRONG!!!, this should hash the fucking value, not the god dammned entire hashmap of values");
+	return (int) fnv_1a(header->bytes, header->n_items*header->itemsize) % header->mapping_capacity;
 }
 
 int map_len(void *this) {