diff --git a/t/Builder.t b/t/Builder.t
index 61ab27500..0ef079cef 100644
--- a/t/Builder.t
+++ b/t/Builder.t
@@ -1,5 +1,12 @@
 #!/usr/bin/perl -w
 
+BEGIN {
+    if( $ENV{PERL_CORE} ) {
+        chdir 't';
+        @INC = '../lib';
+    }
+}
+
 use Test::Builder;
 my $Test = Test::Builder->new;
 
diff --git a/t/More.t b/t/More.t
index 15ffdaa0b..bee2fb4c8 100644
--- a/t/More.t
+++ b/t/More.t
@@ -1,5 +1,12 @@
 #!perl -w
 
+BEGIN {
+    if( $ENV{PERL_CORE} ) {
+        chdir 't';
+        @INC = '../lib';
+    }
+}
+
 use Test::More tests => 37;
 
 # Make sure we don't mess with $@ or $!.  Test at bottom.
diff --git a/t/buffer.t b/t/buffer.t
index fe03ca046..6039e4a6f 100644
--- a/t/buffer.t
+++ b/t/buffer.t
@@ -1,5 +1,12 @@
 #!/usr/bin/perl
 
+BEGIN {
+    if( $ENV{PERL_CORE} ) {
+        chdir 't';
+        @INC = '../lib';
+    }
+}
+
 # Ensure that intermixed prints to STDOUT and tests come out in the
 # right order (ie. no buffering problems).
 
diff --git a/t/diag.t b/t/diag.t
index 6bb366d3d..0d6769b79 100644
--- a/t/diag.t
+++ b/t/diag.t
@@ -1,5 +1,12 @@
 #!perl -w
 
+BEGIN {
+    if( $ENV{PERL_CORE} ) {
+        chdir 't';
+        @INC = '../lib';
+    }
+}
+
 use strict;
 
 use Test::More tests => 5;
diff --git a/t/exit.t b/t/exit.t
index 12a362219..dcc456527 100644
--- a/t/exit.t
+++ b/t/exit.t
@@ -1,6 +1,13 @@
 # Can't use Test.pm, that's a 5.005 thing.
 package My::Test;
 
+BEGIN {
+    if( $ENV{PERL_CORE} ) {
+        chdir 't';
+        @INC = '../lib';
+    }
+}
+
 unless( eval { require File::Spec } ) {
     print "1..0 # Skip Need File::Spec to run this test\n";
     exit 0;
@@ -47,7 +54,8 @@ my %Tests = (
 
 print "1..".keys(%Tests)."\n";
 
-my $lib = File::Spec->catdir(qw(t lib Test Simple sample_tests));
+chdir 't';
+my $lib = File::Spec->catdir(qw(lib Test Simple sample_tests));
 while( my($test_name, $exit_codes) = each %Tests ) {
     my($exit_code) = $exit_codes->[$IsVMS ? 1 : 0];
 
@@ -63,7 +71,7 @@ while( my($test_name, $exit_codes) = each %Tests ) {
     }
 
     my $file = File::Spec->catfile($lib, $test_name);
-    my $wait_stat = system(qq{$Perl -"Iblib/lib" $file});
+    my $wait_stat = system(qq{$Perl -"I../blib/lib" -"I../lib" -"I../t/lib" $file});
     my $actual_exit = $wait_stat >> 8;
 
     My::Test::ok( $actual_exit == $exit_code, 
diff --git a/t/extra.t b/t/extra.t
index e3b0510c8..1ed94adb7 100644
--- a/t/extra.t
+++ b/t/extra.t
@@ -1,5 +1,12 @@
 #!perl -w
 
+BEGIN {
+    if( $ENV{PERL_CORE} ) {
+        chdir 't';
+        @INC = '../lib';
+    }
+}
+
 # Can't use Test.pm, that's a 5.005 thing.
 package My::Test;
 
@@ -23,7 +30,8 @@ package main;
 
 require Test::Simple;
 
-push @INC, 't/lib/';
+chdir 't';
+push @INC, '../t/lib/';
 require Test::Simple::Catch;
 my($out, $err) = Test::Simple::Catch::caught();
 
diff --git a/t/fail-like.t b/t/fail-like.t
index fa07f06f6..13367633c 100644
--- a/t/fail-like.t
+++ b/t/fail-like.t
@@ -7,12 +7,20 @@ BEGIN {
     }
 }
 
+BEGIN {
+    if( $ENV{PERL_CORE} ) {
+        chdir 't';
+        @INC = ('../lib', 'lib');
+    }
+    else {
+        unshift @INC, 't/lib';
+    }
+}
 
 # There was a bug with like() involving a qr// not failing properly.
 # This tests against that.
 
 use strict;
-use lib 't/lib';
 
 require Test::Simple::Catch;
 my($out, $err) = Test::Simple::Catch::caught();
diff --git a/t/fail-more.t b/t/fail-more.t
index 1299a5dd2..6fd88c8ee 100644
--- a/t/fail-more.t
+++ b/t/fail-more.t
@@ -1,7 +1,16 @@
 #!perl -w
 
+BEGIN {
+    if( $ENV{PERL_CORE} ) {
+        chdir 't';
+        @INC = ('../lib', 'lib');
+    }
+    else {
+        unshift @INC, 't/lib';
+    }
+}
+
 use strict;
-use lib 't/lib';
 
 require Test::Simple::Catch;
 my($out, $err) = Test::Simple::Catch::caught();
diff --git a/t/fail.t b/t/fail.t
index 9a722991a..a041ab0eb 100644
--- a/t/fail.t
+++ b/t/fail.t
@@ -1,7 +1,16 @@
 #!perl -w
 
+BEGIN {
+    if( $ENV{PERL_CORE} ) {
+        chdir 't';
+        @INC = ('../lib', 'lib');
+    }
+    else {
+        unshift @INC, 't/lib';
+    }
+}
+
 use strict;
-use lib qw(t/lib);
 
 require Test::Simple::Catch;
 my($out, $err) = Test::Simple::Catch::caught();
diff --git a/t/filehandles.t b/t/filehandles.t
index 3b3c553dc..dfea4ba48 100644
--- a/t/filehandles.t
+++ b/t/filehandles.t
@@ -1,5 +1,12 @@
 #!perl -w
 
+BEGIN {
+    if( $ENV{PERL_CORE} ) {
+        chdir 't';
+        @INC = '../lib';
+    }
+}
+
 use Test::More tests => 1;
 
 tie *STDOUT, "Dev::Null" or die $!;
diff --git a/t/import.t b/t/import.t
index 468c62fd0..68a36138b 100644
--- a/t/import.t
+++ b/t/import.t
@@ -1,3 +1,11 @@
+BEGIN {
+    if( $ENV{PERL_CORE} ) {
+        chdir 't';
+        @INC = '../lib';
+    }
+}
+
+
 use Test::More tests => 2, import => [qw(!fail)];
 
 can_ok(__PACKAGE__, qw(ok pass like isa_ok));
diff --git a/t/is_deeply.t b/t/is_deeply.t
index 3fbc4fbbf..5291fb82c 100644
--- a/t/is_deeply.t
+++ b/t/is_deeply.t
@@ -1,7 +1,16 @@
 #!/usr/bin/perl -w
 
+BEGIN {
+    if( $ENV{PERL_CORE} ) {
+        chdir 't';
+        @INC = ('../lib', 'lib');
+    }
+    else {
+        unshift @INC, 't/lib';
+    }
+}
+
 use strict;
-use lib qw(t/lib);
 
 use Test::Builder;
 require Test::Simple::Catch;
diff --git a/t/missing.t b/t/missing.t
index a8861bbbe..7f451804b 100644
--- a/t/missing.t
+++ b/t/missing.t
@@ -1,3 +1,13 @@
+BEGIN {
+    if( $ENV{PERL_CORE} ) {
+        chdir 't';
+        @INC = ('../lib', 'lib');
+    }
+    else {
+        unshift @INC, 't/lib';
+    }
+}
+
 # Can't use Test.pm, that's a 5.005 thing.
 package My::Test;
 
@@ -21,7 +31,6 @@ package main;
 
 require Test::Simple;
 
-push @INC, 't/lib';
 require Test::Simple::Catch;
 my($out, $err) = Test::Simple::Catch::caught();
 
diff --git a/t/no_ending.t b/t/no_ending.t
index d3ea2756f..97e968e28 100644
--- a/t/no_ending.t
+++ b/t/no_ending.t
@@ -1,5 +1,12 @@
 use Test::Builder;
 
+BEGIN {
+    if( $ENV{PERL_CORE} ) {
+        chdir 't';
+        @INC = '../lib';
+    }
+}
+
 BEGIN {
     my $t = Test::Builder->new;
     $t->no_ending(1);
diff --git a/t/no_header.t b/t/no_header.t
index 1acdb0cc7..93e6bec34 100644
--- a/t/no_header.t
+++ b/t/no_header.t
@@ -1,3 +1,10 @@
+BEGIN {
+    if( $ENV{PERL_CORE} ) {
+        chdir 't';
+        @INC = '../lib';
+    }
+}
+
 use Test::Builder;
 
 # STDOUT must be unbuffered else our prints might come out after
diff --git a/t/no_plan.t b/t/no_plan.t
index 4fdca4591..c0af2d464 100644
--- a/t/no_plan.t
+++ b/t/no_plan.t
@@ -1,3 +1,13 @@
+BEGIN {
+    if( $ENV{PERL_CORE} ) {
+        chdir 't';
+        @INC = ('../lib', 'lib');
+    }
+    else {
+        unshift @INC, 't/lib';
+    }
+}
+
 # Can't use Test.pm, that's a 5.005 thing.
 package My::Test;
 
@@ -21,7 +31,6 @@ package main;
 
 require Test::Simple;
 
-push @INC, 't/lib';
 require Test::Simple::Catch;
 my($out, $err) = Test::Simple::Catch::caught();
 
diff --git a/t/output.t b/t/output.t
index 958ccc706..82dea2883 100644
--- a/t/output.t
+++ b/t/output.t
@@ -1,6 +1,11 @@
 #!perl -w
 
-chdir 't' if -d 't';
+BEGIN {
+    if( $ENV{PERL_CORE} ) {
+        chdir 't';
+        @INC = '../lib';
+    }
+}
 
 # Can't use Test.pm, that's a 5.005 thing.
 print "1..3\n";
diff --git a/t/plan.t b/t/plan.t
index f2d6785ff..a7b26246a 100644
--- a/t/plan.t
+++ b/t/plan.t
@@ -1,3 +1,10 @@
+BEGIN {
+    if( $ENV{PERL_CORE} ) {
+        chdir 't';
+        @INC = '../lib';
+    }
+}
+
 use Test::More;
 
 plan tests => 2;
diff --git a/t/plan_is_noplan.t b/t/plan_is_noplan.t
index d3587356b..1ab2a0e8b 100644
--- a/t/plan_is_noplan.t
+++ b/t/plan_is_noplan.t
@@ -1,8 +1,23 @@
+BEGIN {
+    if( $ENV{PERL_CORE} ) {
+        chdir 't';
+        @INC = ('../lib', 'lib');
+    }
+    else {
+        unshift @INC, 't/lib';
+    }
+}
+
 # Can't use Test.pm, that's a 5.005 thing.
 package My::Test;
 
-# This feature requires a fairly new version of Test::Harness
 BEGIN {
+    if( !$ENV{HARNESS_ACTIVE} && $ENV{PERL_CORE} ) {
+        print "1..0 # Skipped: Won't work with t/TEST\n";
+        exit 0;
+    }
+
+    # This feature requires a fairly new version of Test::Harness
     require Test::Harness;
     if( $Test::Harness::VERSION < 1.20 ) {
         print "1..0 # Skipped: Need Test::Harness 1.20 or up\n";
@@ -30,7 +45,6 @@ package main;
 
 require Test::Simple;
 
-push @INC, 't/lib';
 require Test::Simple::Catch;
 my($out, $err) = Test::Simple::Catch::caught();
 
diff --git a/t/plan_no_plan.t b/t/plan_no_plan.t
index ca2978a30..b39b101cc 100644
--- a/t/plan_no_plan.t
+++ b/t/plan_no_plan.t
@@ -1,5 +1,18 @@
+BEGIN {
+    if( $ENV{PERL_CORE} ) {
+        chdir 't';
+        @INC = '../lib';
+    }
+}
+
 use Test::More;
 
+BEGIN {
+    if( !$ENV{HARNESS_ACTIVE} && $ENV{PERL_CORE} ) {
+        plan skip_all => "Won't work with t/TEST";
+    }
+}
+
 BEGIN {
     require Test::Harness;
 }
diff --git a/t/plan_skip_all.t b/t/plan_skip_all.t
index 75f66789a..528df5f50 100644
--- a/t/plan_skip_all.t
+++ b/t/plan_skip_all.t
@@ -1,3 +1,10 @@
+BEGIN {
+    if( $ENV{PERL_CORE} ) {
+        chdir 't';
+        @INC = '../lib';
+    }
+}
+
 use Test::More;
 
 plan skip_all => 'Just testing plan & skip_all';
diff --git a/t/simple.t b/t/simple.t
index 7f4f1f42d..7297e9d6d 100644
--- a/t/simple.t
+++ b/t/simple.t
@@ -1,3 +1,10 @@
+BEGIN {
+    if( $ENV{PERL_CORE} ) {
+        chdir 't';
+        @INC = '../lib';
+    }
+}
+
 use strict;
 
 BEGIN { $| = 1; $^W = 1; }
diff --git a/t/skip.t b/t/skip.t
index 4de7e7bda..526c5acd8 100644
--- a/t/skip.t
+++ b/t/skip.t
@@ -1,5 +1,12 @@
 #!perl -w
 
+BEGIN {
+    if( $ENV{PERL_CORE} ) {
+        chdir 't';
+        @INC = '../lib';
+    }
+}
+
 use Test::More tests => 15;
 
 # If we skip with the same name, Test::Harness will report it back and
diff --git a/t/skipall.t b/t/skipall.t
index c818f4d51..6f255e21c 100644
--- a/t/skipall.t
+++ b/t/skipall.t
@@ -1,3 +1,13 @@
+BEGIN {
+    if( $ENV{PERL_CORE} ) {
+        chdir 't';
+        @INC = ('../lib', 'lib');
+    }
+    else {
+        unshift @INC, 't/lib';
+    }
+}   
+
 use strict;
 
 # Can't use Test.pm, that's a 5.005 thing.
@@ -22,7 +32,6 @@ sub ok ($;$) {
 package main;
 require Test::More;
 
-push @INC, 't/lib';
 require Test::Simple::Catch;
 my($out, $err) = Test::Simple::Catch::caught();
 
diff --git a/t/todo.t b/t/todo.t
index 607fdb945..31ceb5f63 100644
--- a/t/todo.t
+++ b/t/todo.t
@@ -1,5 +1,12 @@
 #!perl -w
 
+BEGIN {
+    if( $ENV{PERL_CORE} ) {
+        chdir 't';
+        @INC = '../lib';
+    }
+}
+
 BEGIN {
     require Test::Harness;
     use Test::More;
diff --git a/t/undef.t b/t/undef.t
index 7e5290ffa..525126484 100644
--- a/t/undef.t
+++ b/t/undef.t
@@ -1,3 +1,10 @@
+BEGIN {
+    if( $ENV{PERL_CORE} ) {
+        chdir 't';
+        @INC = '../lib';
+    }
+}
+
 use strict;
 use Test::More tests => 12;
 
diff --git a/t/use_ok.t b/t/use_ok.t
index 17e0c30e7..f1d7bed6b 100644
--- a/t/use_ok.t
+++ b/t/use_ok.t
@@ -1,3 +1,10 @@
+BEGIN {
+    if( $ENV{PERL_CORE} ) {
+        chdir 't';
+        @INC = '../lib';
+    }
+}
+
 use Test::More tests => 7;
 
 # Using Symbol because it's core and exports lots of stuff.
diff --git a/t/useing.t b/t/useing.t
index eadc4b3c3..c4ce50712 100644
--- a/t/useing.t
+++ b/t/useing.t
@@ -1,3 +1,10 @@
+BEGIN {
+    if( $ENV{PERL_CORE} ) {
+        chdir 't';
+        @INC = '../lib';
+    }
+}
+
 use Test::More tests => 5;
 
 require_ok('Test::Builder');