diff --git a/test/test_bit_stream.cpp b/test/test_bit_stream.cpp
index c0cbd2512..7ed5979dd 100644
--- a/test/test_bit_stream.cpp
+++ b/test/test_bit_stream.cpp
@@ -930,8 +930,8 @@ namespace
     //*************************************************************************
     TEST(put_get_multiple_variable_size)
     {
-      char c1 = 26;             // 6 bits
-      char c2 = -10;            // 7 bits
+      int8_t c1 = 26;             // 6 bits
+      int8_t c2 = -10;            // 7 bits
       unsigned short s1 = 6742; // 13 bits
       unsigned short s2 = 1878; // 11 bits
       int32_t i1 = 2448037L;     // 23 bits
@@ -983,8 +983,8 @@ namespace
 
       bit_stream.restart();
 
-      char rc1 = 0;
-      char rc2 = 0;
+      int8_t rc1 = 0;
+      int8_t rc2 = 0;
       unsigned short rs1 = 0;
       unsigned short rs2 = 0;
       int32_t ri1 = 0;
diff --git a/test/test_bit_stream_reader_big_endian.cpp b/test/test_bit_stream_reader_big_endian.cpp
index 4cdf3d299..9c099085c 100644
--- a/test/test_bit_stream_reader_big_endian.cpp
+++ b/test/test_bit_stream_reader_big_endian.cpp
@@ -210,7 +210,7 @@ namespace
     TEST(test_read_int8_t)
     {
       std::array<char, 4U> storage = { char(0x01), char(0x5A), char(0xA5), char(0xFF) };
-      std::array<char, 4U> expected = { int8_t(0x01), int8_t(0x5A), int8_t(0xA5), int8_t(0xFF) };
+      std::array<int8_t, 4U> expected = { int8_t(0x01), int8_t(0x5A), int8_t(0xA5), int8_t(0xFF) };
 
       etl::bit_stream_reader bit_stream(storage.data(), storage.size(), etl::endian::big);
 
@@ -246,7 +246,7 @@ namespace
     TEST(test_read_checked_int8_t_using_non_member_function)
     {
       std::array<char, 4U> storage = { char(0x01), char(0x5A), char(0xA5), char(0xFF) };
-      std::array<char, 4U> expected = { int8_t(0x01), int8_t(0x5A), int8_t(0xA5), int8_t(0xFF) };
+      std::array<int8_t, 4U> expected = { int8_t(0x01), int8_t(0x5A), int8_t(0xA5), int8_t(0xFF) };
 
       etl::bit_stream_reader bit_stream(storage.data(), storage.size(), etl::endian::big);
 
@@ -282,7 +282,7 @@ namespace
     TEST(test_read_unchecked_int8_t_using_non_member_function)
     {
       std::array<char, 4U> storage = { char(0x01), char(0x5A), char(0xA5), char(0xFF) };
-      std::array<char, 4U> expected = { int8_t(0x01), int8_t(0x5A), int8_t(0xA5), int8_t(0xFF) };
+      std::array<int8_t, 4U> expected = { int8_t(0x01), int8_t(0x5A), int8_t(0xA5), int8_t(0xFF) };
 
       etl::bit_stream_reader bit_stream(storage.data(), storage.size(), etl::endian::big);
 
@@ -307,7 +307,7 @@ namespace
     TEST(test_read_int8_t_5bits)
     {
       std::array<char, 3U> storage = { char(0x0E), char(0x8B), char(0xF0) };
-      std::array<char, 4U> expected = { int8_t(0x01), int8_t(0xFA), int8_t(0x05), int8_t(0xFF) };
+      std::array<int8_t, 4U> expected = { int8_t(0x01), int8_t(0xFA), int8_t(0x05), int8_t(0xFF) };
 
       etl::bit_stream_reader bit_stream(storage.data(), storage.size(), etl::endian::big);
 
diff --git a/test/test_bresenham_line.cpp b/test/test_bresenham_line.cpp
index 96f5e231c..e350e894f 100644
--- a/test/test_bresenham_line.cpp
+++ b/test/test_bresenham_line.cpp
@@ -44,7 +44,7 @@ namespace etl
 
 namespace
 {
-  using Value = char;
+  using Value = int8_t;
 
   using Point = etl::coordinate_2d<Value>;
 
diff --git a/test/test_correlation.cpp b/test/test_correlation.cpp
index 82f2d0327..aeed9f759 100644
--- a/test/test_correlation.cpp
+++ b/test/test_correlation.cpp
@@ -34,17 +34,17 @@ SOFTWARE.
 
 namespace
 {
-  std::array<char, 10> input_c
+  std::array<int8_t, 10> input_c
   {
     0, 1, 2, 3, 4, 5, 6, 7, 8, 9
   };
 
-  std::array<char, 10> input_c_flat
+  std::array<int8_t, 10> input_c_flat
   {
     0, 0, 0, 0, 0, 0, 0, 0, 0, 0
   };
 
-  std::array<char, 10> input_c_inv
+  std::array<int8_t, 10> input_c_inv
   {
     0, -1, -2, -3, -4, -5, -6, -7, -8, -9
   };
@@ -120,21 +120,21 @@ namespace
       double covariance_result;
 
       // Negative correlation.
-      etl::correlation<etl::correlation_type::Population, char, int32_t> correlation1(input_c.begin(), input_c.end(), input_c_inv.begin());
+      etl::correlation<etl::correlation_type::Population, int8_t, int32_t> correlation1(input_c.begin(), input_c.end(), input_c_inv.begin());
       correlation_result = correlation1;
       CHECK_CLOSE(-1.0, correlation_result, 0.1);
       covariance_result = correlation1.get_covariance();
       CHECK_CLOSE(-8.25, covariance_result, 0.1);
 
       // Zero correlation
-      etl::correlation<etl::correlation_type::Population, char, int32_t> correlation2(input_c.begin(), input_c.end(), input_c_flat.begin());
+      etl::correlation<etl::correlation_type::Population, int8_t, int32_t> correlation2(input_c.begin(), input_c.end(), input_c_flat.begin());
       correlation_result = correlation2;
       CHECK_CLOSE(0.0, correlation_result, 0.1);
       covariance_result = correlation2.get_covariance();
       CHECK_CLOSE(0.0, covariance_result, 0.1);
 
       // Positive correlation.
-      etl::correlation<etl::correlation_type::Population, char, int32_t> correlation3(input_c.begin(), input_c.end(), input_c.begin());
+      etl::correlation<etl::correlation_type::Population, int8_t, int32_t> correlation3(input_c.begin(), input_c.end(), input_c.begin());
       correlation_result = correlation3;
       CHECK_CLOSE(1.0, correlation_result, 0.1);
       covariance_result = correlation3.get_covariance();
@@ -148,21 +148,21 @@ namespace
       double covariance_result;
 
       // Negative correlation.
-      etl::correlation<etl::correlation_type::Sample, char, int32_t> correlation1(input_c.begin(), input_c.end(), input_c_inv.begin());
+      etl::correlation<etl::correlation_type::Sample, int8_t, int32_t> correlation1(input_c.begin(), input_c.end(), input_c_inv.begin());
       correlation_result = correlation1;
       CHECK_CLOSE(-1.0, correlation_result, 0.1);
       covariance_result = correlation1.get_covariance();
       CHECK_CLOSE(-9.17, covariance_result, 0.1);
 
       // Zero correlation
-      etl::correlation<etl::correlation_type::Sample, char, int32_t> correlation2(input_c.begin(), input_c.end(), input_c_flat.begin());
+      etl::correlation<etl::correlation_type::Sample, int8_t, int32_t> correlation2(input_c.begin(), input_c.end(), input_c_flat.begin());
       correlation_result = correlation2;
       CHECK_CLOSE(0.0, correlation_result, 0.1);
       covariance_result = correlation2.get_covariance();
       CHECK_CLOSE(0.0, covariance_result, 0.1);
 
       // Positive correlation.
-      etl::correlation<etl::correlation_type::Sample, char, int32_t> correlation3(input_c.begin(), input_c.end(), input_c.begin());
+      etl::correlation<etl::correlation_type::Sample, int8_t, int32_t> correlation3(input_c.begin(), input_c.end(), input_c.begin());
       correlation_result = correlation3;
       CHECK_CLOSE(1.0, correlation_result, 0.1);
       covariance_result = correlation3.get_covariance();
diff --git a/test/test_covariance.cpp b/test/test_covariance.cpp
index a127616c8..6ce84d726 100644
--- a/test/test_covariance.cpp
+++ b/test/test_covariance.cpp
@@ -34,17 +34,17 @@ SOFTWARE.
 
 namespace
 {
-  std::array<char, 10> input_c
+  std::array<int8_t, 10> input_c
   {
     0, 1, 2, 3, 4, 5, 6, 7, 8, 9
   };
 
-  std::array<char, 10> input_c_flat
+  std::array<int8_t, 10> input_c_flat
   {
     0, 0, 0, 0, 0, 0, 0, 0, 0, 0
   };
 
-  std::array<char, 10> input_c_inv
+  std::array<int8_t, 10> input_c_inv
   {
     0, -1, -2, -3, -4, -5, -6, -7, -8, -9
   };
@@ -119,17 +119,17 @@ namespace
       double covariance_result;
 
       // Negative covariance.
-      etl::covariance<etl::covariance_type::Population, char, int32_t> covariance1(input_c.begin(), input_c.end(), input_c_inv.begin());
+      etl::covariance<etl::covariance_type::Population, int8_t, int32_t> covariance1(input_c.begin(), input_c.end(), input_c_inv.begin());
       covariance_result = covariance1.get_covariance();
       CHECK_CLOSE(-8.25, covariance_result, 0.1);
 
       // Zero covariance
-      etl::covariance<etl::covariance_type::Population, char, int32_t> covariance2(input_c.begin(), input_c.end(), input_c_flat.begin());
+      etl::covariance<etl::covariance_type::Population, int8_t, int32_t> covariance2(input_c.begin(), input_c.end(), input_c_flat.begin());
       covariance_result = covariance2.get_covariance();
       CHECK_CLOSE(0.0, covariance_result, 0.1);
 
       // Positive covariance.
-      etl::covariance<etl::covariance_type::Population, char, int32_t> covariance3(input_c.begin(), input_c.end(), input_c.begin());
+      etl::covariance<etl::covariance_type::Population, int8_t, int32_t> covariance3(input_c.begin(), input_c.end(), input_c.begin());
       covariance_result = covariance3.get_covariance();
       CHECK_CLOSE(8.25, covariance_result, 0.1);
     }
@@ -140,17 +140,17 @@ namespace
       double covariance_result;
 
       // Negative covariance.
-      etl::covariance<etl::covariance_type::Sample, char, int32_t> covariance1(input_c.begin(), input_c.end(), input_c_inv.begin());
+      etl::covariance<etl::covariance_type::Sample, int8_t, int32_t> covariance1(input_c.begin(), input_c.end(), input_c_inv.begin());
       covariance_result = covariance1.get_covariance();
       CHECK_CLOSE(-9.17, covariance_result, 0.1);
 
       // Zero covariance
-      etl::covariance<etl::covariance_type::Sample, char, int32_t> covariance2(input_c.begin(), input_c.end(), input_c_flat.begin());
+      etl::covariance<etl::covariance_type::Sample, int8_t, int32_t> covariance2(input_c.begin(), input_c.end(), input_c_flat.begin());
       covariance_result = covariance2.get_covariance();
       CHECK_CLOSE(0.0, covariance_result, 0.1);
 
       // Positive covariance.
-      etl::covariance<etl::covariance_type::Sample, char, int32_t> covariance3(input_c.begin(), input_c.end(), input_c.begin());
+      etl::covariance<etl::covariance_type::Sample, int8_t, int32_t> covariance3(input_c.begin(), input_c.end(), input_c.begin());
       covariance_result = covariance3.get_covariance();
       CHECK_CLOSE(9.17, covariance_result, 0.1);
     }
diff --git a/test/test_rms.cpp b/test/test_rms.cpp
index cbc198841..39ae6753e 100644
--- a/test/test_rms.cpp
+++ b/test/test_rms.cpp
@@ -34,7 +34,7 @@ SOFTWARE.
 
 namespace
 {
-  std::array<char, 18> input_c
+  std::array<int8_t, 18> input_c
   {
     // Sawtooth wave
     0, 1, 2, 3, 4, 5, 6, 7, 8, 9, -8, -7, -6, -5, -4, -3, -2, -1
@@ -52,7 +52,7 @@ namespace
     //*************************************************************************
     TEST(test_char_rms)
     {
-      etl::rms<char, int> rms(input_c.begin(), input_c.end());
+      etl::rms<int8_t, int> rms(input_c.begin(), input_c.end());
       double result = rms.get_rms();
 
       CHECK_CLOSE(5.21, result, 0.05);