diff --git a/tests/test_cobs_decode_tinyframe.cc b/tests/test_cobs_decode_tinyframe.cc
index ffa933d..e4e07fe 100644
--- a/tests/test_cobs_decode_tinyframe.cc
+++ b/tests/test_cobs_decode_tinyframe.cc
@@ -176,7 +176,7 @@ TEST_CASE("Decode: Inplace == External") {
   SUBCASE("Fill with one/zero pattern") {
     for (auto i{ 0u }; i < inplace.size() - 2; ++i) {
       inplace[0] = COBS_TINYFRAME_SENTINEL_VALUE;
-      for (auto j = 1u; j < i; ++j) {
+      for (auto j{ 1u }; j < i; ++j) {
         inplace[j] = (j & 1) ^ 1;
       }
       inplace[i + 1] = COBS_TINYFRAME_SENTINEL_VALUE;
diff --git a/tests/test_cobs_encode_inc.cc b/tests/test_cobs_encode_inc.cc
index f23e4fc..9239c11 100644
--- a/tests/test_cobs_encode_inc.cc
+++ b/tests/test_cobs_encode_inc.cc
@@ -40,9 +40,9 @@ TEST_CASE("cobs_encode_inc") {
                       .code_idx = 0,
                       .code = 0,
                       .need_advance = 0 };
-  size_t const enc_max{ 1024 };
+  size_t constexpr enc_max{ 1024 };
   byte_vec_t enc_buf(enc_max);
-  size_t const dec_max{ 1024 };
+  size_t constexpr dec_max{ 1024 };
   byte_vec_t dec_buf(dec_max);
 
   REQUIRE(cobs_encode_inc_begin(enc_buf.data(), enc_max, &ctx) == COBS_RET_SUCCESS);
@@ -136,7 +136,7 @@ TEST_CASE("cobs_encode_inc") {
 
 TEST_CASE("cobs_encode_inc_end") {
   cobs_enc_ctx_t ctx;
-  size_t const enc_max{ 1024 };
+  size_t constexpr enc_max{ 1024 };
   byte_vec_t enc_buf(enc_max);
   size_t enc_len;
 
@@ -218,9 +218,9 @@ void require_equal(byte_vec_t const &v1, byte_vec_t const &v2) {
 
 TEST_CASE("Single/multi-encode equivalences") {
   cobs_enc_ctx_t ctx;
-  size_t const enc_max{ 4096 };
+  size_t constexpr enc_max{ 4096 };
   byte_vec_t enc_buf(enc_max);
-  size_t const dec_max{ 4096 };
+  size_t constexpr dec_max{ 4096 };
   byte_vec_t dec_buf(dec_max);
 
   REQUIRE(cobs_encode_inc_begin(enc_buf.data(), enc_max, &ctx) == COBS_RET_SUCCESS);
@@ -288,7 +288,7 @@ TEST_CASE("Single/multi-encode equivalences") {
   }
 
   SUBCASE("Header / payload split") {
-    byte_t const h[]{ 0x02, 0x03, 0xCC, 0xDF, 0x13, 0x49 };
+    byte_t constexpr h[]{ 0x02, 0x03, 0xCC, 0xDF, 0x13, 0x49 };
 
     dec_buf.resize(400);
     std::iota(std::begin(dec_buf), std::end(dec_buf), byte_t{ 0x01 });
diff --git a/tests/test_cobs_encode_tinyframe.cc b/tests/test_cobs_encode_tinyframe.cc
index 4cfd92d..2abe2e0 100644
--- a/tests/test_cobs_encode_tinyframe.cc
+++ b/tests/test_cobs_encode_tinyframe.cc
@@ -5,7 +5,7 @@
 #include <cstring>
 #include <numeric>
 
-static constexpr byte_t CSV = COBS_TINYFRAME_SENTINEL_VALUE;
+static constexpr byte_t CSV{ COBS_TINYFRAME_SENTINEL_VALUE };
 
 namespace {
 cobs_ret_t cobs_encode_vec(byte_vec_t &v) {
@@ -148,30 +148,30 @@ TEST_CASE("Encode: Inplace == External") {
   byte_t inplace[COBS_TINYFRAME_SAFE_BUFFER_SIZE];
 
   SUBCASE("Fill with zeros") {
-    for (auto i = 0u; i < sizeof(inplace) - 2; ++i) {
+    for (auto i{ 0u }; i < sizeof(inplace) - 2; ++i) {
       fill_inplace(inplace, i, 0x00);
       verify_encode_inplace(inplace, i);
     }
   }
 
   SUBCASE("Fill with nonzeros") {
-    for (auto i = 0u; i < sizeof(inplace) - 2; ++i) {
+    for (auto i{ 0u }; i < sizeof(inplace) - 2; ++i) {
       fill_inplace(inplace, i, 0x01);
       verify_encode_inplace(inplace, i);
     }
   }
 
   SUBCASE("Fill with 0xFF") {
-    for (auto i = 0u; i < sizeof(inplace) - 2; ++i) {
+    for (auto i{ 0u }; i < sizeof(inplace) - 2; ++i) {
       fill_inplace(inplace, i, 0xFF);
       verify_encode_inplace(inplace, i);
     }
   }
 
   SUBCASE("Fill with zero/one pattern") {
-    for (auto i = 0u; i < sizeof(inplace) - 2; ++i) {
+    for (auto i{ 0u }; i < sizeof(inplace) - 2; ++i) {
       inplace[0] = COBS_TINYFRAME_SENTINEL_VALUE;
-      for (auto j = 1u; j < i; ++j) {
+      for (auto j{ 1u }; j < i; ++j) {
         inplace[j] = j & 1;
       }
       inplace[i + 1] = COBS_TINYFRAME_SENTINEL_VALUE;
@@ -180,9 +180,9 @@ TEST_CASE("Encode: Inplace == External") {
   }
 
   SUBCASE("Fill with one/zero pattern") {
-    for (auto i = 0u; i < sizeof(inplace) - 2; ++i) {
+    for (auto i{ 0u }; i < sizeof(inplace) - 2; ++i) {
       inplace[0] = COBS_TINYFRAME_SENTINEL_VALUE;
-      for (auto j = 1u; j < i; ++j) {
+      for (auto j{ 1u }; j < i; ++j) {
         inplace[j] = (j & 1) ^ 1;
       }
       inplace[i + 1] = COBS_TINYFRAME_SENTINEL_VALUE;