diff --git a/tests/basictest.cpp b/tests/basictest.cpp
index 5f61df6..44572ea 100644
--- a/tests/basictest.cpp
+++ b/tests/basictest.cpp
@@ -3,8 +3,13 @@
 #include <doctest/doctest.h>
 
 #include "fast_float/fast_float.h"
+#include <cmath>
+#include <cstdio>
 #include <iomanip>
+#include <ios>
+#include <limits>
 #include <string>
+#include <system_error>
 
 #ifndef SUPPLEMENTAL_TEST_DATA_DIR
 #define SUPPLEMENTAL_TEST_DATA_DIR "data/"
diff --git a/tests/example_comma_test.cpp b/tests/example_comma_test.cpp
index 93f7f8b..12f488d 100644
--- a/tests/example_comma_test.cpp
+++ b/tests/example_comma_test.cpp
@@ -1,6 +1,8 @@
 
 #include "fast_float/fast_float.h"
 #include <iostream>
+#include <string>
+#include <system_error>
  
 int main() {
     const std::string input =  "3,1416 xyz ";
diff --git a/tests/example_test.cpp b/tests/example_test.cpp
index 7d97bb9..db1bae8 100644
--- a/tests/example_test.cpp
+++ b/tests/example_test.cpp
@@ -1,6 +1,8 @@
 
 #include "fast_float/fast_float.h"
 #include <iostream>
+#include <string>
+#include <system_error>
  
 int main() {
     const std::string input =  "3.1416 xyz ";
diff --git a/tests/exhaustive32.cpp b/tests/exhaustive32.cpp
index 879d1e2..9e1e42f 100644
--- a/tests/exhaustive32.cpp
+++ b/tests/exhaustive32.cpp
@@ -1,9 +1,13 @@
 
 #include "fast_float/fast_float.h"
 
-#include <iostream>
 #include <cassert>
 #include <cmath>
+#include <cstdio>
+#include <ios>
+#include <iostream>
+#include <limits>
+#include <system_error>
 
 template <typename T> char *to_string(T d, char *buffer) {
   auto written = std::snprintf(buffer, 64, "%.*e",
diff --git a/tests/exhaustive32_64.cpp b/tests/exhaustive32_64.cpp
index 50aebd7..e02757b 100644
--- a/tests/exhaustive32_64.cpp
+++ b/tests/exhaustive32_64.cpp
@@ -1,9 +1,14 @@
 
 #include "fast_float/fast_float.h"
 
-#include <iostream>
 #include <cassert>
 #include <cmath>
+#include <cstdio>
+#include <ios>
+#include <iostream>
+#include <limits>
+#include <string>
+#include <system_error>
 
 template <typename T> char *to_string(T d, char *buffer) {
   auto written = std::snprintf(buffer, 64, "%.*e",
diff --git a/tests/exhaustive32_midpoint.cpp b/tests/exhaustive32_midpoint.cpp
index cfcb541..f64f4e4 100644
--- a/tests/exhaustive32_midpoint.cpp
+++ b/tests/exhaustive32_midpoint.cpp
@@ -1,8 +1,12 @@
 #include "fast_float/fast_float.h"
 
-#include <iostream>
 #include <cassert>
 #include <cmath>
+#include <cstdio>
+#include <ios>
+#include <iostream>
+#include <limits>
+#include <stdexcept>
 
 #if defined(__CYGWIN__) || defined(__MINGW32__) || defined(__MINGW64__) 
 // Anything at all that is related to cygwin, msys and so forth will
diff --git a/tests/long_exhaustive32.cpp b/tests/long_exhaustive32.cpp
index 683200c..0a6b53d 100644
--- a/tests/long_exhaustive32.cpp
+++ b/tests/long_exhaustive32.cpp
@@ -1,9 +1,12 @@
 
 #include "fast_float/fast_float.h"
 
-#include <iostream>
 #include <cassert>
 #include <cmath>
+#include <cstdio>
+#include <ios>
+#include <iostream>
+#include <system_error>
 
 template <typename T> char *to_string(T d, char *buffer) {
   auto written = std::snprintf(buffer, 128, "%.*e",
diff --git a/tests/long_exhaustive32_64.cpp b/tests/long_exhaustive32_64.cpp
index 0a58895..cea8497 100644
--- a/tests/long_exhaustive32_64.cpp
+++ b/tests/long_exhaustive32_64.cpp
@@ -1,8 +1,10 @@
 #include "fast_float/fast_float.h"
 
-#include <iostream>
 #include <cassert>
 #include <cmath>
+#include <cstdio>
+#include <ios>
+#include <iostream>
 
 template <typename T> char *to_string(T d, char *buffer) {
   auto written = std::snprintf(buffer, 128, "%.*e",
diff --git a/tests/long_random64.cpp b/tests/long_random64.cpp
index e5abe8f..a6680e8 100644
--- a/tests/long_random64.cpp
+++ b/tests/long_random64.cpp
@@ -1,8 +1,11 @@
 #include "fast_float/fast_float.h"
 
-#include <iostream>
 #include <cassert>
 #include <cmath>
+#include <cstdio>
+#include <ios>
+#include <iostream>
+#include <system_error>
 
 template <typename T> char *to_string(T d, char *buffer) {
   auto written = std::snprintf(buffer, 128, "%.*e",
diff --git a/tests/long_test.cpp b/tests/long_test.cpp
index 4af8d50..36b9210 100644
--- a/tests/long_test.cpp
+++ b/tests/long_test.cpp
@@ -1,6 +1,10 @@
 #include "fast_float/fast_float.h"
 
+#include <cctype>
 #include <iostream>
+#include <stdexcept>
+#include <string>
+#include <system_error>
 #include <vector>
 
 inline void Assert(bool Assertion) {
diff --git a/tests/powersoffive_hardround.cpp b/tests/powersoffive_hardround.cpp
index 6258be5..09b95bd 100644
--- a/tests/powersoffive_hardround.cpp
+++ b/tests/powersoffive_hardround.cpp
@@ -1,8 +1,12 @@
 #include "fast_float/fast_float.h"
 
+#include <ios>
 #include <iostream>
 #include <random>
 #include <sstream>
+#include <string>
+#include <system_error>
+#include <utility>
 #include <vector>
 
 
@@ -11,7 +15,6 @@
 // always use this fallback because we cannot rely on it behaving as normal
 // gcc.
 #include <locale>
-#include <sstream>
 // workaround for CYGWIN
 double cygwin_strtod_l(const char* start, char** end) {
     double d;
diff --git a/tests/random64.cpp b/tests/random64.cpp
index 5abc4f8..0775993 100644
--- a/tests/random64.cpp
+++ b/tests/random64.cpp
@@ -1,8 +1,12 @@
 #include "fast_float/fast_float.h"
 
-#include <iostream>
 #include <cassert>
 #include <cmath>
+#include <cstdio>
+#include <ios>
+#include <iostream>
+#include <limits>
+#include <system_error>
 
 template <typename T> char *to_string(T d, char *buffer) {
   auto written = std::snprintf(buffer, 64, "%.*e",
diff --git a/tests/random_string.cpp b/tests/random_string.cpp
index 8f367e0..8cabf5f 100644
--- a/tests/random_string.cpp
+++ b/tests/random_string.cpp
@@ -1,8 +1,11 @@
 #include "fast_float/fast_float.h"
 
-#include <iostream>
 #include <cstdint>
+#include <ios>
+#include <iostream>
 #include <random>
+#include <system_error>
+#include <utility>
 
 #if defined(__CYGWIN__) || defined(__MINGW32__) || defined(__MINGW64__)  || defined(sun) || defined(__sun)
 // Anything at all that is related to cygwin, msys and so forth will
diff --git a/tests/short_random_string.cpp b/tests/short_random_string.cpp
index c71fbe4..3051b74 100644
--- a/tests/short_random_string.cpp
+++ b/tests/short_random_string.cpp
@@ -1,7 +1,11 @@
 #include "fast_float/fast_float.h"
-#include <iostream>
+
 #include <cstdint>
+#include <ios>
+#include <iostream>
 #include <random>
+#include <system_error>
+#include <utility>
 
 #if defined(__CYGWIN__) || defined(__MINGW32__) || defined(__MINGW64__)  || defined(sun) || defined(__sun)
 // Anything at all that is related to cygwin, msys and so forth will
diff --git a/tests/string_test.cpp b/tests/string_test.cpp
index 53f17a4..05871db 100644
--- a/tests/string_test.cpp
+++ b/tests/string_test.cpp
@@ -1,5 +1,12 @@
 #include "fast_float/fast_float.h"
+
+#include <cctype>
+#include <cstdio>
 #include <iostream>
+#include <limits>
+#include <stdexcept>
+#include <string>
+#include <system_error>
 #include <vector>
 
 #if defined(__CYGWIN__) || defined(__MINGW32__) || defined(__MINGW64__)  || defined(sun) || defined(__sun)