diff --git a/crypto/pkcs7/pkcs7_internal_bio_test.cc b/crypto/pkcs7/pkcs7_internal_bio_test.cc
index 355bb84b5bc..16debd15b27 100644
--- a/crypto/pkcs7/pkcs7_internal_bio_test.cc
+++ b/crypto/pkcs7/pkcs7_internal_bio_test.cc
@@ -113,7 +113,7 @@ TEST(PKCS7Test, CipherBIO) {
   EXPECT_TRUE(BIO_get_cipher_status(bio_cipher.get()));
   EXPECT_EQ(Bytes(pt, sizeof(pt)), Bytes(pt_decrypted, sizeof(pt_decrypted)));
 
-  // TODO [childw]
+  // TODO [childw] variable read/write sizes
   bio_cipher.reset(BIO_new(BIO_f_cipher()));
   ASSERT_TRUE(bio_cipher);
   EXPECT_TRUE(BIO_get_cipher_ctx(bio_cipher.get(), &ctx));
@@ -122,7 +122,6 @@ TEST(PKCS7Test, CipherBIO) {
   bio_mem.reset(BIO_new(BIO_s_mem()));
   ASSERT_TRUE(bio_mem);
   ASSERT_TRUE(BIO_push(bio_cipher.get(), bio_mem.get()));
-
   std::vector<uint8_t> pt_vec, ct_vec, decrypted_pt_vec;
   uint8_t buff[1024*1024];
   for (size_t wsize : (size_t[]){1, 3, 7, 8, 64, 7, 0, 923, sizeof(buff), 1, 8}) {
@@ -136,7 +135,6 @@ TEST(PKCS7Test, CipherBIO) {
     size_t bytes_read = BIO_read(bio_mem.get(), buff, sizeof(buff));
     ct_vec.insert(ct_vec.end(), buff, buff + bytes_read);
   }
-
   EXPECT_TRUE(BIO_reset(bio_cipher.get()));  // also resets owned |bio_mem|
   EXPECT_TRUE(BIO_write(bio_mem.get(), ct_vec.data(), ct_vec.size()));  // replace ct
   bio_mem.release();  // |bio_cipher| took ownership
@@ -150,4 +148,43 @@ TEST(PKCS7Test, CipherBIO) {
   EXPECT_EQ(pt_vec.size(), decrypted_pt_vec.size());
   EXPECT_EQ(Bytes(pt_vec.data(), pt_vec.size()),
             Bytes(decrypted_pt_vec.data(), decrypted_pt_vec.size()));
+
+  // TODO [childw] explain induce write failure
+  pt_vec.clear();
+  decrypted_pt_vec.clear();
+  bio_cipher.reset(BIO_new(BIO_f_cipher()));
+  ASSERT_TRUE(bio_cipher);
+  EXPECT_TRUE(BIO_get_cipher_ctx(bio_cipher.get(), &ctx));
+  ASSERT_TRUE(
+      EVP_CipherInit_ex(ctx, EVP_aes_128_gcm(), NULL, key, iv, /*enc*/ 1));
+  bio_mem.reset(BIO_new(BIO_s_mem()));
+  ASSERT_TRUE(bio_mem);
+  ASSERT_TRUE(BIO_push(bio_cipher.get(), bio_mem.get()));
+  const int wsize = 16;
+  pt_vec.insert(pt_vec.end(), buff, buff + wsize);
+  EXPECT_TRUE(BIO_write(bio_cipher.get(), buff, wsize));
+  EXPECT_EQ(0UL, BIO_wpending(bio_cipher.get()));
+  BIO_set_flags(bio_mem.get(), BIO_FLAGS_MEM_RDONLY);
+  pt_vec.insert(pt_vec.end(), buff, buff + wsize);
+  EXPECT_TRUE(BIO_write(bio_cipher.get(), buff, wsize));
+  BIO_clear_flags(bio_mem.get(), BIO_FLAGS_MEM_RDONLY);
+  EXPECT_LT(0UL, BIO_wpending(bio_cipher.get()));
+  EXPECT_TRUE(BIO_flush(bio_cipher.get()));
+  EXPECT_EQ(0UL, BIO_wpending(bio_cipher.get()));
+  EXPECT_TRUE(BIO_get_cipher_status(bio_cipher.get()));
+  EXPECT_TRUE(BIO_get_cipher_ctx(bio_cipher.get(), &ctx));
+  ASSERT_TRUE(
+      EVP_CipherInit_ex(ctx, EVP_aes_128_gcm(), NULL, key, iv, /*enc*/ 0));
+  decrypted_pt_vec.resize(pt_vec.size());
+  // Must seek back to beginning of file before reading
+  ASSERT_EQ(0, BIO_seek(bio_mem.get(), 0));  // 0 indicates success here
+  EXPECT_TRUE(BIO_read(bio_cipher.get(), decrypted_pt_vec.data(), decrypted_pt_vec.size()));
+  EXPECT_TRUE(BIO_get_cipher_status(bio_cipher.get()));
+  EXPECT_EQ(pt_vec.size(), decrypted_pt_vec.size());
+  EXPECT_EQ(Bytes(pt_vec.data(), pt_vec.size()),
+            Bytes(decrypted_pt_vec.data(), decrypted_pt_vec.size()));
+  bio_mem.release();  // |bio_cipher| took ownership
+
+
+  // TODO [childw] induce read failures?
 }