diff --git a/tests/.gitignore b/tests/.gitignore
index dc17f87..cac870c 100644
--- a/tests/.gitignore
+++ b/tests/.gitignore
@@ -1,3 +1,4 @@
 /test_suite*
 data_files/mpi_write
 data_files/hmac_drbg_seed
+data_files/ctr_drbg_seed
diff --git a/tests/suites/test_suite_ctr_drbg.data b/tests/suites/test_suite_ctr_drbg.data
index 6120bb0..53687ae 100644
--- a/tests/suites/test_suite_ctr_drbg.data
+++ b/tests/suites/test_suite_ctr_drbg.data
@@ -718,6 +718,15 @@
 CTR_DRBG NIST Validation (AES-256 use df,False,256,128,256,256) #14
 ctr_drbg_validate_nopr:"50de72903b9d99764123ffaa0c721e14ad1ab5c46a34c040f25324ba1d937b8ef10467161fcf2978c2a680ac5570c6d2":"5c9954fd0143e62c3bf2d5734052e3c9370f7b9d75c70f58fe33b12e3997ee2c8db84f8467affd7cfd9a9e7ec60da6f31bf9bf32aedf644e4934bd1fc916bc8d":"d5dc4c9fc7171fcbfdaead558a565ffd55d245a58b22ad1666ee05131e33f49e":"ea3114e92e6a19f53b207a0a54cd363a6d053fed0a827f92556f0a8580f7a342":"53686f069b455af4692888d11fac15cf7b4bd38e198de4e62b7098f875198a75":"9fb0df053e0345e5640aa97fedef50a6"
 
+CTR_DRBG entropy usage
+ctr_drbg_entropy_usage:
+
+CTR_DRBG write/update seed file
+ctr_drbg_seed_file:"data_files/ctr_drbg_seed":0
+
+CTR_DRBG write/update seed file
+ctr_drbg_seed_file:"no_such_dir/file":POLARSSL_ERR_CTR_DRBG_FILE_IO_ERROR
+
 CTR_DRBG self test
 ctr_drbg_selftest:
 
diff --git a/tests/suites/test_suite_ctr_drbg.function b/tests/suites/test_suite_ctr_drbg.function
index 1ae763d..5690675 100644
--- a/tests/suites/test_suite_ctr_drbg.function
+++ b/tests/suites/test_suite_ctr_drbg.function
@@ -4,9 +4,9 @@
 int test_offset_idx;
 int entropy_func( void *data, unsigned char *buf, size_t len )
 {
-    unsigned char *p = (unsigned char *) data;
+    const unsigned char *p = (unsigned char *) data;
     memcpy( buf, p + test_offset_idx, len );
-    test_offset_idx += 32;
+    test_offset_idx += len;
     return( 0 );
 }
 /* END_HEADER */
@@ -82,6 +82,88 @@
 }
 /* END_CASE */
 
+/* BEGIN_CASE */
+void ctr_drbg_entropy_usage( )
+{
+    unsigned char out[16];
+    unsigned char add[16];
+    unsigned char entropy[1024];
+    ctr_drbg_context ctx;
+    size_t i, reps = 10;
+    int last_idx;
+
+    test_offset_idx = 0;
+    memset( entropy, 0, sizeof( entropy ) );
+    memset( out, 0, sizeof( out ) );
+    memset( add, 0, sizeof( add ) );
+
+    /* Init must use entropy */
+    last_idx = test_offset_idx;
+    TEST_ASSERT( ctr_drbg_init( &ctx, entropy_func, entropy, NULL, 0 ) == 0 );
+    TEST_ASSERT( last_idx < test_offset_idx );
+
+    /* By default, PR is off and reseed_interval is large,
+     * so the next few calls should not use entropy */
+    last_idx = test_offset_idx;
+    for( i = 0; i < reps; i++ )
+    {
+        TEST_ASSERT( ctr_drbg_random( &ctx, out, sizeof( out ) - 4 ) == 0 );
+        TEST_ASSERT( ctr_drbg_random_with_add( &ctx, out, sizeof( out ) - 4,
+                                                add, sizeof( add ) ) == 0 );
+    }
+    TEST_ASSERT( last_idx == test_offset_idx );
+
+    /* While at it, make sure we didn't write past the requested length */
+    TEST_ASSERT( out[sizeof( out ) - 4] == 0 );
+    TEST_ASSERT( out[sizeof( out ) - 3] == 0 );
+    TEST_ASSERT( out[sizeof( out ) - 2] == 0 );
+    TEST_ASSERT( out[sizeof( out ) - 1] == 0 );
+
+    /* Set reseed_interval to the number of calls done,
+     * so the next call should reseed */
+    ctr_drbg_set_reseed_interval( &ctx, 2 * reps );
+    TEST_ASSERT( ctr_drbg_random( &ctx, out, sizeof( out ) ) == 0 );
+    TEST_ASSERT( last_idx < test_offset_idx );
+
+    /* The new few calls should not reseed */
+    last_idx = test_offset_idx;
+    for( i = 0; i < reps / 2; i++ )
+    {
+        TEST_ASSERT( ctr_drbg_random( &ctx, out, sizeof( out ) ) == 0 );
+        TEST_ASSERT( ctr_drbg_random_with_add( &ctx, out, sizeof( out ) ,
+                                                add, sizeof( add ) ) == 0 );
+    }
+    TEST_ASSERT( last_idx == test_offset_idx );
+
+    /* Now enable PR, so the next few calls should all reseed */
+    ctr_drbg_set_prediction_resistance( &ctx, CTR_DRBG_PR_ON );
+    TEST_ASSERT( ctr_drbg_random( &ctx, out, sizeof( out ) ) == 0 );
+    TEST_ASSERT( last_idx < test_offset_idx );
+
+    /* Finally, check setting entropy_len */
+    ctr_drbg_set_entropy_len( &ctx, 42 );
+    last_idx = test_offset_idx;
+    TEST_ASSERT( ctr_drbg_random( &ctx, out, sizeof( out ) ) == 0 );
+    TEST_ASSERT( test_offset_idx - last_idx == 42 );
+
+    ctr_drbg_set_entropy_len( &ctx, 13 );
+    last_idx = test_offset_idx;
+    TEST_ASSERT( ctr_drbg_random( &ctx, out, sizeof( out ) ) == 0 );
+    TEST_ASSERT( test_offset_idx - last_idx == 13 );
+}
+/* END_CASE */
+
+/* BEGIN_CASE depends_on:POLARSSL_FS_IO */
+void ctr_drbg_seed_file( char *path, int ret )
+{
+    ctr_drbg_context ctx;
+
+    TEST_ASSERT( ctr_drbg_init( &ctx, rnd_std_rand, NULL, NULL, 0 ) == 0 );
+    TEST_ASSERT( ctr_drbg_write_seed_file( &ctx, path ) == ret );
+    TEST_ASSERT( ctr_drbg_update_seed_file( &ctx, path ) == ret );
+}
+/* END_CASE */
+
 /* BEGIN_CASE depends_on:POLARSSL_SELF_TEST */
 void ctr_drbg_selftest( )
 {