diff --git a/t/t4015-diff-whitespace.sh b/t/t4015-diff-whitespace.sh
index eadaf57262..7fb83c8eff 100755
--- a/t/t4015-diff-whitespace.sh
+++ b/t/t4015-diff-whitespace.sh
@@ -16,7 +16,8 @@ test_expect_success "Ray Lehtiniemi's example" '
 	} while (0);
 	EOF
 	git update-index --add x &&
-	before=$(git rev-parse --short $(git hash-object x)) &&
+	old_hash_x=$(git hash-object x) &&
+	before=$(git rev-parse --short "$old_hash_x") &&
 
 	cat <<-\EOF >x &&
 	do
@@ -25,7 +26,8 @@ test_expect_success "Ray Lehtiniemi's example" '
 	}
 	while (0);
 	EOF
-	after=$(git rev-parse --short $(git hash-object x)) &&
+	new_hash_x=$(git hash-object x) &&
+	after=$(git rev-parse --short "$new_hash_x") &&
 
 	cat <<-EOF >expect &&
 	diff --git a/x b/x
@@ -63,7 +65,8 @@ test_expect_success 'another test, without options' '
 	EOF
 
 	git update-index x &&
-	before=$(git rev-parse --short $(git hash-object x)) &&
+	old_hash_x=$(git hash-object x) &&
+	before=$(git rev-parse --short "$old_hash_x") &&
 
 	tr "_" " " <<-\EOF >x &&
 	_	whitespace at beginning
@@ -73,7 +76,8 @@ test_expect_success 'another test, without options' '
 	unchanged line
 	CR at end
 	EOF
-	after=$(git rev-parse --short $(git hash-object x)) &&
+	new_hash_x=$(git hash-object x) &&
+	after=$(git rev-parse --short "$new_hash_x") &&
 
 	tr "Q_" "\015 " <<-EOF >expect &&
 	diff --git a/x b/x
@@ -526,13 +530,15 @@ test_expect_success 'ignore-blank-lines: mix changes and blank lines' '
 test_expect_success 'check mixed spaces and tabs in indent' '
 	# This is indented with SP HT SP.
 	echo " 	 foo();" >x &&
-	git diff --check | grep "space before tab in indent"
+	test_must_fail git diff --check >check &&
+	grep "space before tab in indent" check
 '
 
 test_expect_success 'check mixed tabs and spaces in indent' '
 	# This is indented with HT SP HT.
 	echo "	 	foo();" >x &&
-	git diff --check | grep "space before tab in indent"
+	test_must_fail git diff --check >check &&
+	grep "space before tab in indent" check
 '
 
 test_expect_success 'check with no whitespace errors' '
@@ -753,20 +759,23 @@ test_expect_success 'check tab-in-indent excluded from wildcard whitespace attri
 test_expect_success 'line numbers in --check output are correct' '
 	echo "" >x &&
 	echo "foo(); " >>x &&
-	git diff --check | grep "x:2:"
+	test_must_fail git diff --check >check &&
+	grep "x:2:" check
 '
 
 test_expect_success 'checkdiff detects new trailing blank lines (1)' '
 	echo "foo();" >x &&
 	echo "" >>x &&
-	git diff --check | grep "new blank line"
+	test_must_fail git diff --check >check &&
+	grep "new blank line" check
 '
 
 test_expect_success 'checkdiff detects new trailing blank lines (2)' '
 	{ echo a; echo b; echo; echo; } >x &&
 	git add x &&
 	{ echo a; echo; echo; echo; echo; } >x &&
-	git diff --check | grep "new blank line"
+	test_must_fail git diff --check >check &&
+	grep "new blank line" check
 '
 
 test_expect_success 'checkdiff allows new blank lines' '
@@ -794,14 +803,16 @@ test_expect_success 'whitespace-only changes reported across renames' '
 	git reset --hard &&
 	for i in 1 2 3 4 5 6 7 8 9; do echo "$i$i$i$i$i$i"; done >x &&
 	git add x &&
-	before=$(git rev-parse --short $(git hash-object x)) &&
+	hash_x=$(git hash-object x) &&
+	before=$(git rev-parse --short "$hash_x") &&
 	git commit -m "base" &&
 	sed -e "5s/^/ /" x >z &&
 	git rm x &&
 	git add z &&
-	after=$(git rev-parse --short $(git hash-object z)) &&
-	git diff -w -M --cached |
-	sed -e "/^similarity index /s/[0-9][0-9]*/NUM/" >actual &&
+	hash_z=$(git hash-object z) &&
+	after=$(git rev-parse --short "$hash_z") &&
+	git diff -w -M --cached >actual.raw &&
+	sed -e "/^similarity index /s/[0-9][0-9]*/NUM/" actual.raw >actual &&
 	cat <<-EOF >expect &&
 	diff --git a/x b/z
 	similarity index NUM%
@@ -840,7 +851,8 @@ test_expect_success 'combined diff with autocrlf conversion' '
 	git config core.autocrlf true &&
 	test_must_fail git merge master &&
 
-	git diff | sed -e "1,/^@@@/d" >actual &&
+	git diff >actual.raw &&
+	sed -e "1,/^@@@/d" actual.raw >actual &&
 	! grep "^-" actual
 
 '
@@ -864,11 +876,14 @@ test_expect_success 'diff that introduces a line with only tabs' '
 	git config core.whitespace blank-at-eol &&
 	git reset --hard &&
 	echo "test" >x &&
-	before=$(git rev-parse --short $(git hash-object x)) &&
+	old_hash_x=$(git hash-object x) &&
+	before=$(git rev-parse --short "$old_hash_x") &&
 	git commit -m "initial" x &&
 	echo "{NTN}" | tr "NT" "\n\t" >>x &&
-	after=$(git rev-parse --short $(git hash-object x)) &&
-	git diff --color | test_decode_color >current &&
+	new_hash_x=$(git hash-object x) &&
+	after=$(git rev-parse --short "$new_hash_x") &&
+	git diff --color >current.raw &&
+	test_decode_color <current.raw >current &&
 
 	cat >expected <<-EOF &&
 	<BOLD>diff --git a/x b/x<RESET>
@@ -891,17 +906,19 @@ test_expect_success 'diff that introduces and removes ws breakages' '
 		echo "0. blank-at-eol " &&
 		echo "1. blank-at-eol "
 	} >x &&
-	before=$(git rev-parse --short $(git hash-object x)) &&
+	old_hash_x=$(git hash-object x) &&
+	before=$(git rev-parse --short "$old_hash_x") &&
 	git commit -a --allow-empty -m preimage &&
 	{
 		echo "0. blank-at-eol " &&
 		echo "1. still-blank-at-eol " &&
 		echo "2. and a new line "
 	} >x &&
-	after=$(git rev-parse --short $(git hash-object x)) &&
+	new_hash_x=$(git hash-object x) &&
+	after=$(git rev-parse --short "$new_hash_x") &&
 
-	git diff --color |
-	test_decode_color >current &&
+	git diff --color >current.raw &&
+	test_decode_color <current.raw >current &&
 
 	cat >expected <<-EOF &&
 	<BOLD>diff --git a/x b/x<RESET>
@@ -925,14 +942,16 @@ test_expect_success 'ws-error-highlight test setup' '
 		echo "0. blank-at-eol " &&
 		echo "1. blank-at-eol "
 	} >x &&
-	before=$(git rev-parse --short $(git hash-object x)) &&
+	old_hash_x=$(git hash-object x) &&
+	before=$(git rev-parse --short "$old_hash_x") &&
 	git commit -a --allow-empty -m preimage &&
 	{
 		echo "0. blank-at-eol " &&
 		echo "1. still-blank-at-eol " &&
 		echo "2. and a new line "
 	} >x &&
-	after=$(git rev-parse --short $(git hash-object x)) &&
+	new_hash_x=$(git hash-object x) &&
+	after=$(git rev-parse --short "$new_hash_x") &&
 
 	cat >expect.default-old <<-EOF &&
 	<BOLD>diff --git a/x b/x<RESET>
@@ -974,32 +993,32 @@ test_expect_success 'ws-error-highlight test setup' '
 
 test_expect_success 'test --ws-error-highlight option' '
 
-	git diff --color --ws-error-highlight=default,old |
-	test_decode_color >current &&
+	git diff --color --ws-error-highlight=default,old >current.raw &&
+	test_decode_color <current.raw >current &&
 	test_cmp expect.default-old current &&
 
-	git diff --color --ws-error-highlight=all |
-	test_decode_color >current &&
+	git diff --color --ws-error-highlight=all >current.raw &&
+	test_decode_color <current.raw >current &&
 	test_cmp expect.all current &&
 
-	git diff --color --ws-error-highlight=none |
-	test_decode_color >current &&
+	git diff --color --ws-error-highlight=none >current.raw &&
+	test_decode_color <current.raw >current &&
 	test_cmp expect.none current
 
 '
 
 test_expect_success 'test diff.wsErrorHighlight config' '
 
-	git -c diff.wsErrorHighlight=default,old diff --color |
-	test_decode_color >current &&
+	git -c diff.wsErrorHighlight=default,old diff --color >current.raw &&
+	test_decode_color <current.raw >current &&
 	test_cmp expect.default-old current &&
 
-	git -c diff.wsErrorHighlight=all diff --color |
-	test_decode_color >current &&
+	git -c diff.wsErrorHighlight=all diff --color >current.raw &&
+	test_decode_color <current.raw >current &&
 	test_cmp expect.all current &&
 
-	git -c diff.wsErrorHighlight=none diff --color |
-	test_decode_color >current &&
+	git -c diff.wsErrorHighlight=none diff --color >current.raw &&
+	test_decode_color <current.raw >current &&
 	test_cmp expect.none current
 
 '
@@ -1007,18 +1026,18 @@ test_expect_success 'test diff.wsErrorHighlight config' '
 test_expect_success 'option overrides diff.wsErrorHighlight' '
 
 	git -c diff.wsErrorHighlight=none \
-		diff --color --ws-error-highlight=default,old |
-	test_decode_color >current &&
+		diff --color --ws-error-highlight=default,old >current.raw &&
+	test_decode_color <current.raw >current &&
 	test_cmp expect.default-old current &&
 
 	git -c diff.wsErrorHighlight=default \
-		diff --color --ws-error-highlight=all |
-	test_decode_color >current &&
+		diff --color --ws-error-highlight=all >current.raw &&
+	test_decode_color <current.raw >current &&
 	test_cmp expect.all current &&
 
 	git -c diff.wsErrorHighlight=all \
-		diff --color --ws-error-highlight=none |
-	test_decode_color >current &&
+		diff --color --ws-error-highlight=none >current.raw &&
+	test_decode_color <current.raw >current &&
 	test_cmp expect.none current
 
 '
@@ -1038,7 +1057,8 @@ test_expect_success 'detect moved code, complete file' '
 	git mv test.c main.c &&
 	test_config color.diff.oldMoved "normal red" &&
 	test_config color.diff.newMoved "normal green" &&
-	git diff HEAD --color-moved=zebra --color --no-renames | test_decode_color >actual &&
+	git diff HEAD --color-moved=zebra --color --no-renames >actual.raw &&
+	test_decode_color <actual.raw >actual &&
 	cat >expected <<-EOF &&
 	<BOLD>diff --git a/main.c b/main.c<RESET>
 	<BOLD>new file mode 100644<RESET>
@@ -1141,9 +1161,12 @@ test_expect_success 'detect malicious moved code, inside file' '
 			bar();
 		}
 	EOF
-	after_main=$(git rev-parse --short $(git hash-object main.c)) &&
-	after_test=$(git rev-parse --short $(git hash-object test.c)) &&
-	git diff HEAD --no-renames --color-moved=zebra --color | test_decode_color >actual &&
+	hash_main=$(git hash-object main.c) &&
+	after_main=$(git rev-parse --short "$hash_main") &&
+	hash_test=$(git hash-object test.c) &&
+	after_test=$(git rev-parse --short "$hash_test") &&
+	git diff HEAD --no-renames --color-moved=zebra --color >actual.raw &&
+	test_decode_color <actual.raw >actual &&
 	cat <<-EOF >expected &&
 	<BOLD>diff --git a/main.c b/main.c<RESET>
 	<BOLD>index $before_main..$after_main 100644<RESET>
@@ -1192,7 +1215,8 @@ test_expect_success 'plain moved code, inside file' '
 	test_config color.diff.oldMovedAlternative "blue" &&
 	test_config color.diff.newMovedAlternative "yellow" &&
 	# needs previous test as setup
-	git diff HEAD --no-renames --color-moved=plain --color | test_decode_color >actual &&
+	git diff HEAD --no-renames --color-moved=plain --color >actual.raw &&
+	test_decode_color <actual.raw >actual &&
 	cat <<-EOF >expected &&
 	<BOLD>diff --git a/main.c b/main.c<RESET>
 	<BOLD>index $before_main..$after_main 100644<RESET>
@@ -1771,7 +1795,8 @@ test_expect_success 'move detection with submodules' '
 	! grep BRED decoded_actual &&
 
 	# nor did we mess with it another way
-	git diff --submodule=diff --color | test_decode_color >expect &&
+	git diff --submodule=diff --color >expect.raw &&
+	test_decode_color <expect.raw >expect &&
 	test_cmp expect decoded_actual &&
 	rm -rf bananas &&
 	git submodule deinit bananas
