diff --git a/mm/damon/vaddr-test.h b/mm/damon/vaddr-test.h
index ecfd0b2ed222..3097ef9c662a 100644
--- a/mm/damon/vaddr-test.h
+++ b/mm/damon/vaddr-test.h
@@ -252,59 +252,62 @@ static void damon_test_apply_three_regions4(struct kunit *test)
 			new_three_regions, expected, ARRAY_SIZE(expected));
 }
 
+static void damon_test_split_evenly_fail(struct kunit *test,
+		unsigned long start, unsigned long end, unsigned int nr_pieces)
+{
+	struct damon_target *t = damon_new_target(42);
+	struct damon_region *r = damon_new_region(start, end);
+
+	damon_add_region(r, t);
+	KUNIT_EXPECT_EQ(test,
+			damon_va_evenly_split_region(t, r, nr_pieces), -EINVAL);
+	KUNIT_EXPECT_EQ(test, damon_nr_regions(t), 1u);
+
+	damon_for_each_region(r, t) {
+		KUNIT_EXPECT_EQ(test, r->ar.start, start);
+		KUNIT_EXPECT_EQ(test, r->ar.end, end);
+	}
+
+	damon_free_target(t);
+}
+
+static void damon_test_split_evenly_succ(struct kunit *test,
+	unsigned long start, unsigned long end, unsigned int nr_pieces)
+{
+	struct damon_target *t = damon_new_target(42);
+	struct damon_region *r = damon_new_region(start, end);
+	unsigned long expected_width = (end - start) / nr_pieces;
+	unsigned long i = 0;
+
+	damon_add_region(r, t);
+	KUNIT_EXPECT_EQ(test,
+			damon_va_evenly_split_region(t, r, nr_pieces), 0);
+	KUNIT_EXPECT_EQ(test, damon_nr_regions(t), nr_pieces);
+
+	damon_for_each_region(r, t) {
+		if (i == nr_pieces - 1)
+			break;
+		KUNIT_EXPECT_EQ(test,
+				r->ar.start, start + i++ * expected_width);
+		KUNIT_EXPECT_EQ(test, r->ar.end, start + i * expected_width);
+	}
+	KUNIT_EXPECT_EQ(test, r->ar.start, start + i * expected_width);
+	KUNIT_EXPECT_EQ(test, r->ar.end, end);
+	damon_free_target(t);
+}
+
 static void damon_test_split_evenly(struct kunit *test)
 {
 	struct damon_ctx *c = damon_new_ctx();
-	struct damon_target *t;
-	struct damon_region *r;
-	unsigned long i;
 
 	KUNIT_EXPECT_EQ(test, damon_va_evenly_split_region(NULL, NULL, 5),
 			-EINVAL);
 
-	t = damon_new_target(42);
-	r = damon_new_region(0, 100);
-	KUNIT_EXPECT_EQ(test, damon_va_evenly_split_region(t, r, 0), -EINVAL);
+	damon_test_split_evenly_fail(test, 0, 100, 0);
+	damon_test_split_evenly_succ(test, 0, 100, 10);
+	damon_test_split_evenly_succ(test, 5, 59, 5);
+	damon_test_split_evenly_fail(test, 5, 6, 2);
 
-	damon_add_region(r, t);
-	KUNIT_EXPECT_EQ(test, damon_va_evenly_split_region(t, r, 10), 0);
-	KUNIT_EXPECT_EQ(test, damon_nr_regions(t), 10u);
-
-	i = 0;
-	damon_for_each_region(r, t) {
-		KUNIT_EXPECT_EQ(test, r->ar.start, i++ * 10);
-		KUNIT_EXPECT_EQ(test, r->ar.end, i * 10);
-	}
-	damon_free_target(t);
-
-	t = damon_new_target(42);
-	r = damon_new_region(5, 59);
-	damon_add_region(r, t);
-	KUNIT_EXPECT_EQ(test, damon_va_evenly_split_region(t, r, 5), 0);
-	KUNIT_EXPECT_EQ(test, damon_nr_regions(t), 5u);
-
-	i = 0;
-	damon_for_each_region(r, t) {
-		if (i == 4)
-			break;
-		KUNIT_EXPECT_EQ(test, r->ar.start, 5 + 10 * i++);
-		KUNIT_EXPECT_EQ(test, r->ar.end, 5 + 10 * i);
-	}
-	KUNIT_EXPECT_EQ(test, r->ar.start, 5 + 10 * i);
-	KUNIT_EXPECT_EQ(test, r->ar.end, 59ul);
-	damon_free_target(t);
-
-	t = damon_new_target(42);
-	r = damon_new_region(5, 6);
-	damon_add_region(r, t);
-	KUNIT_EXPECT_EQ(test, damon_va_evenly_split_region(t, r, 2), -EINVAL);
-	KUNIT_EXPECT_EQ(test, damon_nr_regions(t), 1u);
-
-	damon_for_each_region(r, t) {
-		KUNIT_EXPECT_EQ(test, r->ar.start, 5ul);
-		KUNIT_EXPECT_EQ(test, r->ar.end, 6ul);
-	}
-	damon_free_target(t);
 	damon_destroy_ctx(c);
 }