tests: improve coverage for s2n_stream_cipher_null (#5268)

Co-authored-by: maddeleine <59030281+maddeleine@users.noreply.github.com>
Co-authored-by: Lindsay Stewart <slindsay@amazon.com>

Author: 3 people

tests/unit/s2n_stream_cipher_null_test.c

@@ -30,7 +30,8 @@ int main(int argc, char **argv)
         EXPECT_SUCCESS(s2n_blob_init(&in, array, 9));
         struct s2n_blob out = { 0 };
         EXPECT_SUCCESS(s2n_blob_init(&out, array, 9));
-        EXPECT_SUCCESS(s2n_stream_cipher_null_endecrypt(NULL, &in, &out));
+        struct s2n_session_key session_key = { 0 };
+        EXPECT_SUCCESS(s2n_stream_cipher_null_endecrypt(&session_key, &in, &out));
     };
 
     /* Test that in size > out size fails */
@@ -40,7 +41,8 @@ int main(int argc, char **argv)
         EXPECT_SUCCESS(s2n_blob_init(&in, array, 9));
         struct s2n_blob out = { 0 };
         EXPECT_SUCCESS(s2n_blob_init(&out, array, 8));
-        EXPECT_FAILURE(s2n_stream_cipher_null_endecrypt(NULL, &in, &out));
+        struct s2n_session_key session_key = { 0 };
+        EXPECT_FAILURE(s2n_stream_cipher_null_endecrypt(&session_key, &in, &out));
     };
 
     /* Test that in is copied to out when they are different */
@@ -52,9 +54,34 @@ int main(int argc, char **argv)
         struct s2n_blob out = { 0 };
         EXPECT_SUCCESS(s2n_blob_init(&out, out_array, 9));
         EXPECT_BYTEARRAY_NOT_EQUAL(in_array, out_array, out.size);
-        EXPECT_SUCCESS(s2n_stream_cipher_null_endecrypt(NULL, &in, &out));
+        struct s2n_session_key session_key = { 0 };
+        EXPECT_SUCCESS(s2n_stream_cipher_null_endecrypt(&session_key, &in, &out));
         EXPECT_BYTEARRAY_EQUAL(in_array, out_array, out.size);
     };
 
+    /* Test that null cipher is always available */
+    {
+        EXPECT_TRUE(s2n_stream_cipher_null_available());
+    };
+
+    /* Test that get_key always returns success */
+    {
+        struct s2n_blob in = { 0 };
+        struct s2n_session_key session_key = { 0 };
+        EXPECT_OK(s2n_stream_cipher_null_get_key(&session_key, &in));
+    };
+
+    /* Test that destroy_key always returns success */
+    {
+        struct s2n_session_key session_key = { 0 };
+        EXPECT_OK(s2n_stream_cipher_null_destroy_key(&session_key));
+    };
+
+    /* Test that init always returns success */
+    {
+        struct s2n_session_key session_key = { 0 };
+        EXPECT_OK(s2n_stream_cipher_null_init(&session_key));
+    };
+
     END_TEST();
 }