[PATCH next 3/7] random32: Fix tests for xor -> add change to prandom_u32_state()

[David Laight]

The test vectors check the result of prandom_u32_state() against known
values. The change to prandom_u32_state() to add the four values to
make determining the state not completely trivial breaks this.

Rather than change the test data fix the tests by adding a local
function that combines the four values using xor.

Signed-off-by: David Laight <david.laight.linux@xxxxxxxxx>
---
 lib/tests/random32_kunit.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/lib/tests/random32_kunit.c b/lib/tests/random32_kunit.c
index 0b4af2b09c01..ccf439686fda 100644
--- a/lib/tests/random32_kunit.c
+++ b/lib/tests/random32_kunit.c
@@ -136,6 +136,16 @@ static void prandom_state_test_seed(struct rnd_state *state, u32 seed)
 	state->s4 = __seed(LCG(state->s3), 128U);
 }
 
+/*
+ * prandom_u32_state() adds the values to stop the generator being linear.
+ * To avoid changing the test recover the expected value.
+ */
+static u32 prandom_u32_state_xor(struct rnd_state *state)
+{
+	prandom_u32_state(state);
+	return state->s1 ^ state->s2 ^ state->s3 ^ state->s4;
+}
+
 static void test_prandom_seed_boundary(struct kunit *test)
 {
 	int i;
@@ -144,7 +154,7 @@ static void test_prandom_seed_boundary(struct kunit *test)
 	for (i = 0; i < ARRAY_SIZE(test1); i++) {
 		prandom_state_test_seed(&state, test1[i].seed);
 		prandom_warmup(&state);
-		KUNIT_EXPECT_EQ(test, test1[i].result, prandom_u32_state(&state));
+		KUNIT_EXPECT_EQ(test, test1[i].result, prandom_u32_state_xor(&state));
 	}
 }
 
@@ -160,7 +170,7 @@ static void test_prandom_taus113(struct kunit *test)
 		for (j = 0; j < test2[i].iteration - 1; j++)
 			prandom_u32_state(&state);
 
-		KUNIT_EXPECT_EQ(test, test2[i].result, prandom_u32_state(&state));
+		KUNIT_EXPECT_EQ(test, test2[i].result, prandom_u32_state_xor(&state));
 	}
 }
 
-- 
2.39.5