Add "use warnings"

t/02_clientsim_txt_parsable.t

@@ -4,6 +4,7 @@
 # doesn't have any syntax errors
 
 use strict;
+use warnings;
 use Test::More;
 
 my $tests = 0;

t/03_syntax_check.t

@@ -3,6 +3,7 @@
 # Basics: are there semantic errors which are easy to spot?
 
 use strict;
+use warnings;
 use Test::More;
 
 my $tests = 0;

t/12_diff_opensslversions.t

@@ -5,6 +5,7 @@
 # This runs a basic test with the supplied openssl vs /usr/bin/openssl
 
 use strict;
+use warnings;
 use Test::More;
 use Data::Dumper;
 use Text::Diff;

t/32_isHTML_valid.t

@@ -4,6 +4,7 @@
 # This could be amended by using HTML::Tidy or HTML::Valid
 
 use strict;
+use warnings;
 use Test::More;
 use Data::Dumper;
 use Text::Diff;

t/52_ocsp_revoked.t

@@ -7,6 +7,7 @@
 # We don't use a full run, only the certificate section.
 
 use strict;
+use warnings;
 use Test::More;
 use Data::Dumper;
 use Text::Diff;

t/53_hsts_preload.t

@@ -6,6 +6,7 @@
 # We don't use a full run, only the HTTP header section.
 
 use strict;
+use warnings;
 use Test::More;
 
 my $tests = 0;

t/61_diff_testsslsh.t

@@ -9,6 +9,7 @@
 #
 
 use strict;
+use warnings;
 use Test::More;
 use Data::Dumper;
 use Text::Diff;