diff --git a/.gitignore b/.gitignore
index 344d9f3c..679552e6 100644
--- a/.gitignore
+++ b/.gitignore
@@ -409,3 +409,4 @@ examples/UniquePtrWithPool/Makefile
 examples/UniquePtrWithPool/CMakeCache.txt
 examples/UniquePtrWithPool/UniquePtrWithPool
 test/vs2022/Debug Clang C++20 - Optimised -O2
+include/etl/header_file_list.txt
diff --git a/include/etl/const_set.h b/include/etl/const_set.h
index 20c4b67f..18f36032 100644
--- a/include/etl/const_set.h
+++ b/include/etl/const_set.h
@@ -445,9 +445,6 @@ namespace etl
     using const_iterator  = typename base_t::const_iterator;
     using size_type       = typename base_t::size_type;
 
-    /// Defines the parameter types
-    using const_reference = const key_type&;
-
     static_assert((etl::is_default_constructible<key_type>::value), "key_type must be default constructible");
 
     //*************************************************************************
diff --git a/test/CMakeLists.txt b/test/CMakeLists.txt
index 5840bb35..888fd12c 100644
--- a/test/CMakeLists.txt
+++ b/test/CMakeLists.txt
@@ -12,16 +12,358 @@ project(etl_unit_tests LANGUAGES CXX)
 
 add_executable(etl_tests
 	main.cpp
+	murmurhash3.cpp
+	test_algorithm.cpp
+	test_alignment.cpp
+	test_array.cpp
+	test_array_view.cpp
+	test_array_wrapper.cpp
+	test_atomic.cpp
+	test_base64_RFC2152_decoder.cpp
+	test_base64_RFC2152_encoder.cpp
+	test_base64_RFC3501_decoder.cpp
+	test_base64_RFC3501_encoder.cpp
+	test_base64_RFC4648_decoder_with_no_padding.cpp
+	test_base64_RFC4648_decoder_with_padding.cpp
+	test_base64_RFC4648_encoder_with_no_padding.cpp
+	test_base64_RFC4648_encoder_with_padding.cpp
+	test_base64_RFC4648_URL_decoder_with_no_padding.cpp
+	test_base64_RFC4648_URL_decoder_with_padding.cpp
+	test_base64_RFC4648_URL_encoder_with_no_padding.cpp
+	test_base64_RFC4648_URL_encoder_with_padding.cpp
+	test_binary.cpp
+	test_bip_buffer_spsc_atomic.cpp
+	test_bit.cpp
+	test_bitset_legacy.cpp
+	test_bitset_new_comparisons.cpp
+	test_bitset_new_default_element_type.cpp
+	test_bitset_new_explicit_single_element_type.cpp
+	test_bitset_new_ext_default_element_type.cpp
+	test_bitset_new_ext_explicit_single_element_type.cpp
+	test_bit_stream.cpp
+	test_bit_stream_reader_big_endian.cpp
+	test_bit_stream_reader_little_endian.cpp
+	test_bit_stream_writer_big_endian.cpp
+	test_bit_stream_writer_little_endian.cpp
+	test_bloom_filter.cpp
+	test_bresenham_line.cpp
+	test_bsd_checksum.cpp
+	test_buffer_descriptors.cpp
+	test_byte.cpp
+	test_byte_stream.cpp
+	test_callback_service.cpp
+	test_callback_timer.cpp
+	test_callback_timer_atomic.cpp
+	test_callback_timer_deferred_locked.cpp
+	test_callback_timer_interrupt.cpp
+	test_callback_timer_locked.cpp
+	test_char_traits.cpp
+	test_checksum.cpp
+	test_chrono_clocks.cpp
+	test_chrono_day.cpp
+	test_chrono_duration.cpp
+	test_chrono_hh_mm_ss.cpp
+	test_chrono_literals.cpp
+	test_chrono_month.cpp
+	test_chrono_month_day.cpp
+	test_chrono_month_day_last.cpp
+	test_chrono_month_weekday.cpp
+	test_chrono_month_weekday_last.cpp
+	test_chrono_operators.cpp
+	test_chrono_time_point.cpp
+	test_chrono_weekday.cpp
+	test_chrono_weekday_indexed.cpp
+	test_chrono_weekday_last.cpp
+	test_chrono_year.cpp
+	test_chrono_year_month.cpp
+	test_chrono_year_month_day.cpp
+	test_chrono_year_month_day_last.cpp
+	test_chrono_year_month_weekday.cpp
+	test_chrono_year_month_weekday_last.cpp
+	test_circular_buffer.cpp
+	test_circular_buffer_external_buffer.cpp
+	test_circular_iterator.cpp
+	test_closure.cpp
+	test_closure_constexpr.cpp
+	test_compare.cpp
+	test_constant.cpp
+	test_const_map.cpp
+	test_const_map_constexpr.cpp
+	test_const_map_ext.cpp
+	test_const_map_ext_constexpr.cpp
+	test_const_multimap.cpp
+	test_const_multimap_constexpr.cpp
+	test_const_multimap_ext.cpp
+	test_const_multimap_ext_constexpr.cpp
+	test_const_multiset.cpp
+	test_const_multiset_constexpr.cpp
+	test_const_multiset_ext.cpp
+	test_const_multiset_ext_constexpr.cpp
+	test_const_set.cpp
+	test_const_set_constexpr.cpp
+	test_const_set_ext.cpp
+	test_const_set_ext_constexpr.cpp
+	test_container.cpp
+	test_correlation.cpp
+	test_covariance.cpp
+	test_crc1.cpp
+	test_crc16.cpp
+	test_crc16_a.cpp
+	test_crc16_arc.cpp
+	test_crc16_aug_ccitt.cpp
+	test_crc16_buypass.cpp
+	test_crc16_ccitt.cpp
+	test_crc16_cdma2000.cpp
+	test_crc16_dds110.cpp
+	test_crc16_dectr.cpp
+	test_crc16_dectx.cpp
+	test_crc16_dnp.cpp
+	test_crc16_en13757.cpp
+	test_crc16_genibus.cpp
+	test_crc16_kermit.cpp
+	test_crc16_m17.cpp
+	test_crc16_maxim.cpp
+	test_crc16_mcrf4xx.cpp
+	test_crc16_modbus.cpp
+	test_crc16_opensafety_a.cpp
+	test_crc16_opensafety_b.cpp
+	test_crc16_profibus.cpp
+	test_crc16_riello.cpp
+	test_crc16_t10dif.cpp
+	test_crc16_teledisk.cpp
+	test_crc16_tms37157.cpp
+	test_crc16_usb.cpp
+	test_crc16_x25.cpp
+	test_crc16_xmodem.cpp
+	test_crc32.cpp
+	test_crc32_bzip2.cpp
+	test_crc32_c.cpp
+	test_crc32_d.cpp
+	test_crc32_jamcrc.cpp
+	test_crc32_mpeg2.cpp
+	test_crc32_posix.cpp
+	test_crc32_q.cpp
+	test_crc32_xfer.cpp
+	test_crc64_ecma.cpp
+	test_crc64_iso.cpp
+	test_crc8_ccitt.cpp
+	test_crc8_cdma2000.cpp
+	test_crc8_darc.cpp
+	test_crc8_dvbs2.cpp
+	test_crc8_ebu.cpp
+	test_crc8_icode.cpp
+	test_crc8_itu.cpp
+	test_crc8_j1850.cpp
+	test_crc8_j1850_zero.cpp
+	test_crc8_maxim.cpp
+	test_crc8_nrsc5.cpp
+	test_crc8_opensafety.cpp
+	test_crc8_rohc.cpp
+	test_crc8_wcdma.cpp
+	test_cyclic_value.cpp
+	test_debounce.cpp
+	test_delegate.cpp
+	test_delegate_cpp03.cpp
+	test_delegate_observable.cpp
+	test_delegate_service.cpp
+	test_delegate_service_compile_time.cpp
+	test_delegate_service_cpp03.cpp
+	test_deque.cpp
+	test_endian.cpp
+	test_enum_type.cpp
+	test_error_handler.cpp
+	test_etl_traits.cpp
+	test_exception.cpp
+	test_expected.cpp
+	test_fixed_iterator.cpp
+	test_fixed_sized_memory_block_allocator.cpp
+	test_flags.cpp
+	test_flat_map.cpp
+	test_flat_multimap.cpp
+	test_flat_multiset.cpp
+	test_flat_set.cpp
+	test_fnv_1.cpp
+	test_format_spec.cpp
+	test_forward_list.cpp
+	test_forward_list_shared_pool.cpp
+	test_fsm.cpp
+	test_function.cpp
+	test_functional.cpp
+	test_function_traits.cpp
+	test_gamma.cpp
+	test_hash.cpp
+	test_hfsm.cpp
+	test_hfsm_recurse_to_inner_state_on_start.cpp
+	test_histogram.cpp
+	test_index_of_type.cpp
+	test_indirect_vector.cpp
+	test_indirect_vector_external_buffer.cpp
+	test_instance_count.cpp
+	test_integral_limits.cpp
+	test_intrusive_forward_list.cpp
+	test_intrusive_links.cpp
+	test_intrusive_list.cpp
+	test_intrusive_queue.cpp
+	test_intrusive_stack.cpp
+	test_invert.cpp
+	test_io_port.cpp
+	test_iterator.cpp
+	test_jenkins.cpp
+	test_largest.cpp
+	test_limiter.cpp
+	test_limits.cpp
+	test_list.cpp
+	test_list_shared_pool.cpp
+	test_macros.cpp
+	test_make_string.cpp
+	test_map.cpp
+	test_math.cpp
+	test_math_functions.cpp
+	test_mean.cpp
+	test_memory.cpp
+	test_mem_cast.cpp
+	test_mem_cast_ptr.cpp
+	test_message.cpp
+	test_message_broker.cpp
+	test_message_bus.cpp
+	test_message_packet.cpp
+	test_message_router.cpp
+	test_message_router_registry.cpp
+	test_message_timer.cpp
+	test_message_timer_atomic.cpp
+	test_message_timer_interrupt.cpp
+	test_message_timer_locked.cpp
+	test_multimap.cpp
+	test_multiset.cpp
+	test_multi_array.cpp
+	test_multi_range.cpp
+	test_multi_span.cpp
+	test_multi_vector.cpp
+	test_murmur3.cpp
+	test_not_null_pointer.cpp
+	test_not_null_pointer_constexpr.cpp
+	test_not_null_unique_pointer.cpp
+	test_nth_type.cpp
+	test_numeric.cpp
+	test_observer.cpp
+	test_optional.cpp
+	test_overload.cpp
+	test_packet.cpp
+	test_parameter_pack.cpp
+	test_parameter_type.cpp
+	test_parity_checksum.cpp
+	test_pearson.cpp
+	test_poly_span_dynamic_extent.cpp
+	test_poly_span_fixed_extent.cpp
+	test_pool.cpp
+	test_pool_external_buffer.cpp
+	test_priority_queue.cpp
+	test_pseudo_moving_average.cpp
+	test_quantize.cpp
+	test_queue.cpp
+	test_queue_lockable.cpp
+	test_queue_lockable_small.cpp
+	test_queue_memory_model_small.cpp
+	test_queue_mpmc_mutex.cpp
+	test_queue_mpmc_mutex_small.cpp
+	test_queue_spsc_atomic.cpp
+	test_queue_spsc_atomic_small.cpp
+	test_queue_spsc_isr.cpp
+	test_queue_spsc_isr_small.cpp
+	test_queue_spsc_locked.cpp
+	test_queue_spsc_locked_small.cpp
+	test_random.cpp
+	test_ratio.cpp
+	test_reference_flat_map.cpp
+	test_reference_flat_multimap.cpp
+	test_reference_flat_multiset.cpp
+	test_reference_flat_set.cpp
+	test_rescale.cpp
+	test_result.cpp
+	test_rms.cpp
+	test_rounded_integral_division.cpp
+	test_scaled_rounding.cpp
+	test_set.cpp
+	test_shared_message.cpp
+	test_singleton.cpp
+	test_singleton_base.cpp
+	test_smallest.cpp
+	test_span_dynamic_extent.cpp
+	test_span_fixed_extent.cpp
+	test_stack.cpp
+	test_standard_deviation.cpp
+	test_state_chart.cpp
+	test_state_chart_compile_time.cpp
+	test_state_chart_compile_time_with_data_parameter.cpp
+	test_state_chart_with_data_parameter.cpp
+	test_state_chart_with_rvalue_data_parameter.cpp
 	test_string_char.cpp
 	test_string_char_external_buffer.cpp
+	test_string_stream.cpp
+	test_string_stream_u16.cpp
+	test_string_stream_u32.cpp
+	test_string_stream_u8.cpp
+	test_string_stream_wchar_t.cpp
 	test_string_u16.cpp
 	test_string_u16_external_buffer.cpp
 	test_string_u32.cpp
 	test_string_u32_external_buffer.cpp
 	test_string_u8.cpp
 	test_string_u8_external_buffer.cpp
+	test_string_utilities.cpp
+	test_string_utilities_std.cpp
+	test_string_utilities_std_u16.cpp
+	test_string_utilities_std_u32.cpp
+	test_string_utilities_std_u8.cpp
+	test_string_utilities_std_wchar_t.cpp
+	test_string_utilities_u16.cpp
+	test_string_utilities_u32.cpp
+	test_string_utilities_u8.cpp
+	test_string_utilities_wchar_t.cpp
+	test_string_view.cpp
 	test_string_wchar_t.cpp
 	test_string_wchar_t_external_buffer.cpp
+	test_successor.cpp
+	test_task_scheduler.cpp
+	test_threshold.cpp
+	test_to_arithmetic.cpp
+	test_to_arithmetic_u16.cpp
+	test_to_arithmetic_u32.cpp
+	test_to_arithmetic_u8.cpp
+	test_to_arithmetic_wchar_t.cpp
+	test_to_string.cpp
+	test_to_u16string.cpp
+	test_to_u32string.cpp
+	test_to_u8string.cpp
+	test_to_wstring.cpp
+	test_tuple.cpp
+	test_type_def.cpp
+	test_type_list.cpp
+	test_type_lookup.cpp
+	test_type_select.cpp
+	test_type_traits.cpp
+	test_unaligned_type.cpp
+	test_unaligned_type_ext.cpp
+	test_uncopyable.cpp
+	test_unordered_map.cpp
+	test_unordered_multimap.cpp
+	test_unordered_multiset.cpp
+	test_unordered_set.cpp
+	test_user_type.cpp
+	test_utility.cpp
+	test_variance.cpp
+	test_variant_legacy.cpp
+	test_variant_pool.cpp
+	test_variant_pool_external_buffer.cpp
+	test_variant_variadic.cpp
+	test_vector.cpp
+	test_vector_external_buffer.cpp
+	test_vector_non_trivial.cpp
+	test_vector_pointer.cpp
+	test_vector_pointer_external_buffer.cpp
+	test_visitor.cpp
+	test_xor_checksum.cpp
+	test_xor_rotate_checksum.cpp
   )
 
 target_compile_definitions(etl_tests PRIVATE -DETL_DEBUG)
diff --git a/test/test_const_multiset.cpp b/test/test_const_multiset.cpp
index ae97994b..4e444495 100644
--- a/test/test_const_multiset.cpp
+++ b/test/test_const_multiset.cpp
@@ -86,10 +86,10 @@ namespace
   }
 
   // Equality operator for Key != Key
-  constexpr bool operator !=(const Key& lhs, const Key& rhs) noexcept
-  {
-    return !(lhs.k == rhs.k);
-  }
+  //constexpr bool operator !=(const Key& lhs, const Key& rhs) noexcept
+  //{
+  //  return !(lhs.k == rhs.k);
+  //}
 
 #define TEST_GREATER_THAN
 #ifdef TEST_GREATER_THAN
diff --git a/test/test_const_multiset_constexpr.cpp b/test/test_const_multiset_constexpr.cpp
index d431466a..d9cba6f7 100644
--- a/test/test_const_multiset_constexpr.cpp
+++ b/test/test_const_multiset_constexpr.cpp
@@ -86,10 +86,10 @@ namespace
   }
 
   // Equality operator for Key != Key
-  constexpr bool operator !=(const Key& lhs, const Key& rhs) noexcept
-  {
-    return !(lhs.k == rhs.k);
-  }
+  //constexpr bool operator !=(const Key& lhs, const Key& rhs) noexcept
+  //{
+  //  return !(lhs.k == rhs.k);
+  //}
 
 #define TEST_GREATER_THAN
 #ifdef TEST_GREATER_THAN
diff --git a/test/test_const_multiset_ext.cpp b/test/test_const_multiset_ext.cpp
index a05fef54..44780f81 100644
--- a/test/test_const_multiset_ext.cpp
+++ b/test/test_const_multiset_ext.cpp
@@ -87,10 +87,10 @@ namespace
   }
 
   // Equality operator for Key != Key
-  constexpr bool operator !=(const Key& lhs, const Key& rhs) noexcept
-  {
-    return !(lhs.k == rhs.k);
-  }
+  //constexpr bool operator !=(const Key& lhs, const Key& rhs) noexcept
+  //{
+  //  return !(lhs.k == rhs.k);
+  //}
 
 #define TEST_GREATER_THAN
 #ifdef TEST_GREATER_THAN
diff --git a/test/test_const_multiset_ext_constexpr.cpp b/test/test_const_multiset_ext_constexpr.cpp
index da032198..6d58c18b 100644
--- a/test/test_const_multiset_ext_constexpr.cpp
+++ b/test/test_const_multiset_ext_constexpr.cpp
@@ -86,11 +86,11 @@ namespace
     return (lhs.k == rhs.k);
   }
 
-  // Equality operator for Key != Key
-  constexpr bool operator !=(const Key& lhs, const Key& rhs) noexcept
-  {
-    return !(lhs.k == rhs.k);
-  }
+  //// Equality operator for Key != Key
+  //constexpr bool operator !=(const Key& lhs, const Key& rhs) noexcept
+  //{
+  //  return !(lhs.k == rhs.k);
+  //}
 
 #define TEST_GREATER_THAN
 #ifdef TEST_GREATER_THAN
diff --git a/test/test_const_set.cpp b/test/test_const_set.cpp
index c923a3e2..6e3ec66b 100644
--- a/test/test_const_set.cpp
+++ b/test/test_const_set.cpp
@@ -84,10 +84,10 @@ namespace
   }
 
   // Equality operator for Key != Key
-  constexpr bool operator !=(const Key& lhs, const Key& rhs) noexcept
-  {
-    return !(lhs.k == rhs.k);
-  }
+  //constexpr bool operator !=(const Key& lhs, const Key& rhs) noexcept
+  //{
+  //  return !(lhs.k == rhs.k);
+  //}
 
   #define TEST_GREATER_THAN
   #ifdef TEST_GREATER_THAN
diff --git a/test/test_const_set_constexpr.cpp b/test/test_const_set_constexpr.cpp
index 0e2a0cfa..f8f7c467 100644
--- a/test/test_const_set_constexpr.cpp
+++ b/test/test_const_set_constexpr.cpp
@@ -84,10 +84,10 @@ namespace
   }
 
   // Equality operator for Key != Key
-  constexpr bool operator !=(const Key& lhs, const Key& rhs) noexcept
-  {
-    return !(lhs.k == rhs.k);
-  }
+  //constexpr bool operator !=(const Key& lhs, const Key& rhs) noexcept
+  //{
+  //  return !(lhs.k == rhs.k);
+  //}
 
   #define TEST_GREATER_THAN
   #ifdef TEST_GREATER_THAN
@@ -1129,6 +1129,7 @@ namespace
 
       CHECK_TRUE(equal12);
       CHECK_FALSE(equal13);
+      CHECK_FALSE(equal14);
     }
 
     //*************************************************************************
diff --git a/test/test_const_set_ext.cpp b/test/test_const_set_ext.cpp
index b96fffb4..7f613308 100644
--- a/test/test_const_set_ext.cpp
+++ b/test/test_const_set_ext.cpp
@@ -90,10 +90,10 @@ namespace
   }
 
   // Equality operator for Key != Key
-  constexpr bool operator !=(const Key& lhs, const Key& rhs) noexcept
-  {
-    return !(lhs.k == rhs.k);
-  }
+  //constexpr bool operator !=(const Key& lhs, const Key& rhs) noexcept
+  //{
+  //  return !(lhs.k == rhs.k);
+  //}
 
   #define TEST_GREATER_THAN
   #ifdef TEST_GREATER_THAN
diff --git a/test/test_const_set_ext_constexpr.cpp b/test/test_const_set_ext_constexpr.cpp
index feb15cc7..13ce5216 100644
--- a/test/test_const_set_ext_constexpr.cpp
+++ b/test/test_const_set_ext_constexpr.cpp
@@ -90,10 +90,10 @@ namespace
   }
 
   // Equality operator for Key != Key
-  constexpr bool operator !=(const Key& lhs, const Key& rhs) noexcept
-  {
-    return !(lhs.k == rhs.k);
-  }
+  //constexpr bool operator !=(const Key& lhs, const Key& rhs) noexcept
+  //{
+  //  return !(lhs.k == rhs.k);
+  //}
 
   #define TEST_GREATER_THAN
   #ifdef TEST_GREATER_THAN