diff --git a/src/Makefile.global.in b/src/Makefile.global.in
index 05c54b27def..1e49d8c8c37 100644
--- a/src/Makefile.global.in
+++ b/src/Makefile.global.in
@@ -450,7 +450,7 @@ define prove_installcheck
 rm -rf '$(CURDIR)'/tmp_check
 $(MKDIR_P) '$(CURDIR)'/tmp_check
 cd $(srcdir) && \
-   TESTDIR='$(CURDIR)' PATH="$(bindir):$(CURDIR):$$PATH" \
+   PATH="$(bindir):$(CURDIR):$$PATH" \
    PGPORT='6$(DEF_PGPORT)' top_builddir='$(CURDIR)/$(top_builddir)' \
    PG_REGRESS='$(CURDIR)/$(top_builddir)/src/test/regress/pg_regress' \
    $(PROVE) $(PG_PROVE_FLAGS) $(PROVE_FLAGS) $(if $(PROVE_TESTS),$(PROVE_TESTS),t/*.pl)
@@ -460,7 +460,7 @@ define prove_installcheck
 rm -rf '$(CURDIR)'/tmp_check
 $(MKDIR_P) '$(CURDIR)'/tmp_check
 cd $(srcdir) && \
-   TESTDIR='$(CURDIR)' PATH="$(bindir):$(CURDIR):$$PATH" \
+   PATH="$(bindir):$(CURDIR):$$PATH" \
    PGPORT='6$(DEF_PGPORT)' top_builddir='$(top_builddir)' \
    PG_REGRESS='$(top_builddir)/src/test/regress/pg_regress' \
    $(PROVE) $(PG_PROVE_FLAGS) $(PROVE_FLAGS) $(if $(PROVE_TESTS),$(PROVE_TESTS),t/*.pl)
@@ -471,7 +471,7 @@ define prove_check
 rm -rf '$(CURDIR)'/tmp_check
 $(MKDIR_P) '$(CURDIR)'/tmp_check
 cd $(srcdir) && \
-   TESTDIR='$(CURDIR)' $(with_temp_install) PGPORT='6$(DEF_PGPORT)' \
+   $(with_temp_install) PGPORT='6$(DEF_PGPORT)' \
    PG_REGRESS='$(CURDIR)/$(top_builddir)/src/test/regress/pg_regress' \
    $(PROVE) $(PG_PROVE_FLAGS) $(PROVE_FLAGS) $(if $(PROVE_TESTS),$(PROVE_TESTS),t/*.pl)
 endef
diff --git a/src/bin/psql/t/010_tab_completion.pl b/src/bin/psql/t/010_tab_completion.pl
index 005961f34d4..a86dc78a365 100644
--- a/src/bin/psql/t/010_tab_completion.pl
+++ b/src/bin/psql/t/010_tab_completion.pl
@@ -70,7 +70,7 @@ delete $ENV{LS_COLORS};
 # to run in the build directory so that we can use relative paths to
 # access the tmp_check subdirectory; otherwise the output from filename
 # completion tests is too variable.
-if ($ENV{TESTDIR})
+if ($ENV{TESTDIR} && 0)
 {
 	chdir $ENV{TESTDIR} or die "could not chdir to \"$ENV{TESTDIR}\": $!";
 }
diff --git a/src/test/modules/libpq_pipeline/t/001_libpq_pipeline.pl b/src/test/modules/libpq_pipeline/t/001_libpq_pipeline.pl
index facfec5cad4..2a0eca77440 100644
--- a/src/test/modules/libpq_pipeline/t/001_libpq_pipeline.pl
+++ b/src/test/modules/libpq_pipeline/t/001_libpq_pipeline.pl
@@ -49,9 +49,7 @@ for my $testname (@tests)
 		my $expected;
 		my $result;
 
-		# Hack to allow TESTDIR=. during parallel tap tests
-		my $inputdir = "$ENV{'TESTDIR'}/src/test/modules/libpq_pipeline";
-		$inputdir = "$ENV{'TESTDIR'}" if ! -e $inputdir;
+		my $inputdir = "$ENV{'TESTDIR'}/tmp_check";
 		$expected = slurp_file_eval("$inputdir/traces/$testname.trace");
 		next unless $expected ne "";
 		$result = slurp_file_eval($traceout);
diff --git a/src/test/perl/PostgreSQL/Test/Utils.pm b/src/test/perl/PostgreSQL/Test/Utils.pm
index 57fcb240898..5429de41ed5 100644
--- a/src/test/perl/PostgreSQL/Test/Utils.pm
+++ b/src/test/perl/PostgreSQL/Test/Utils.pm
@@ -184,19 +184,21 @@ INIT
 	# test may still fail, but it's more likely to report useful facts.
 	$SIG{PIPE} = 'IGNORE';
 
-	# Determine output directories, and create them.  The base path is the
-	# TESTDIR environment variable, which is normally set by the invoking
-	# Makefile.
-	$tmp_check = $ENV{TESTDIR} ? "$ENV{TESTDIR}/tmp_check" : "tmp_check";
+	my $test_dir = File::Spec->rel2abs(dirname($0));
+	my $test_name = basename($0);
+	$test_name =~ s/\.[^.]+$//;
+
+	# Determine output directories, and create them.
+	# TODO: set TESTDIR and srcdir?
+	$tmp_check = "$test_dir/tmp_check";
 	$log_path = "$tmp_check/log";
+	$ENV{TESTDIR} = $test_dir;
 
 	mkdir $tmp_check;
 	mkdir $log_path;
 
 	# Open the test log file, whose name depends on the test name.
-	$test_logfile = basename($0);
-	$test_logfile =~ s/\.[^.]+$//;
-	$test_logfile = "$log_path/regress_log_$test_logfile";
+	$test_logfile = "$log_path/regress_log_$test_name";
 	open my $testlog, '>', $test_logfile
 	  or die "could not open STDOUT to logfile \"$test_logfile\": $!";
 
diff --git a/src/tools/msvc/vcregress.pl b/src/tools/msvc/vcregress.pl
index fdb6f44eded..d7794c5766a 100644
--- a/src/tools/msvc/vcregress.pl
+++ b/src/tools/msvc/vcregress.pl
@@ -261,10 +261,8 @@ sub tap_check
 	$ENV{PG_REGRESS}    = "$topdir/$Config/pg_regress/pg_regress";
 	$ENV{REGRESS_SHLIB} = "$topdir/src/test/regress/regress.dll";
 
-	$ENV{TESTDIR} = "$dir";
 	my $module = basename $dir;
-	# add the module build dir as the second element in the PATH
-	$ENV{PATH} =~ s!;!;$topdir/$Config/$module;!;
+	$ENV{VCREGRESS_MODE} = $Config;
 
 	print "============================================================\n";
 	print "Checking @args\n";