Migrate maniadd + readonly + noop behaviour to its own test.

t/Manifest.t

@@ -14,7 +14,7 @@ chdir 't';
 
 use strict;
 
-use Test::More tests => 66;
+use Test::More tests => 64;
 use Cwd;
 
 use File::Spec;
@@ -313,25 +313,6 @@ is_deeply( $files, \%expect, 'maniadd() vs MANIFEST without trailing newline');
 #add_file('MANIFEST'   => 'Makefile.PL');
 #maniadd({ foo => 'bar' });
 
-SKIP: {
-    chmod( 0400, 'MANIFEST' );
-    skip "Can't make MANIFEST read-only", 2 if -w 'MANIFEST' or $Config{osname} eq 'cygwin';
-
-    eval {
-        maniadd({ 'foo' => 'bar' });
-    };
-    is( $@, '',  "maniadd() won't open MANIFEST if it doesn't need to" );
-
-    eval {
-        maniadd({ 'grrrwoof' => 'yippie' });
-    };
-    like( $@, qr/^\Qmaniadd() could not open MANIFEST:\E/,
-                 "maniadd() dies if it can't open the MANIFEST" );
-
-    chmod( 0600, 'MANIFEST' );
-}
-
-
 END {
 	note "remove all files";
 	for my $file ( sort keys %Files ) {

t/maniadd.t

@@ -0,0 +1,53 @@
+use strict;
+use warnings;
+
+use lib 't/lib';
+use ManifestTest qw( catch_warning canon_warning spew runtemp );
+use ExtUtils::Manifest qw( maniadd );
+use Config;
+use Test::More tests => 5;
+
+my $LAST_ERROR;
+
+# Return 1 if it fatalled, undef otherwise.
+# Its almost bash!
+# !fatal = expect not fatal.
+# fatal  = expect fatal
+sub fatal(&) {
+  my ($code) = @_;
+  my ($ok);
+  {
+    local $@;
+    $ok = eval { $code->(); 1 };
+    $LAST_ERROR = $@;
+  }
+  return !$ok;
+}
+
+runtemp "maniadd.unneeded_readonly" => sub {
+  note "Ensuring maniadd does not need to write to a file for existing entries";
+
+  spew( "MANIFEST", "foo #bar\n" );
+SKIP: {
+    chmod( 0400, "MANIFEST" );
+
+    if ( -w "MANIFEST" or $Config{osname} eq "cygwin" ) {
+      skip "Cant make manifest readonly", 5;
+    }
+
+    ok( !fatal { maniadd( { "foo" => "bar" } ) }, "maniadd() wont die adding an existing key" )
+      or diag $LAST_ERROR;
+
+    ok( !-w "MANIFEST", "MANIFEST is still readonly" );
+
+    ok( fatal { maniadd( { "grrrwoof" => "yippie" } ) }, "maniadd will die adding a new key" )
+      or diag $LAST_ERROR;
+
+    like( $LAST_ERROR, qr/^\Qmaniadd() could not open MANIFEST:\E/, "maniadd dies with the expected warning" );
+
+    ok( !-w "MANIFEST", "MANIFEST is still readonly" );
+
+    chmod( 0600, 'MANIFEST' );
+  }
+
+};