tests(export): ensure previous value of variable works correctly

test.sh

@@ -1139,4 +1139,31 @@ expecting <<"EOF"
 - hello' 'world -
 EOF
 
+when_run <<"EOF" "previous variable value in export"
+export VAR=hello
+export VAR=" $VAR and goodbye"
+echo $VAR | cat -e
+EOF
+expecting <<EOF
+hello and goodbye$
+EOF
+
+when_run <<"EOF" "previous variable value in export, but single-quoted"
+export VAR=hello
+export VAR=' $VAR and goodbye'
+echo $VAR | cat -e
+EOF
+expecting <<"EOF"
+$VAR and goodbye$
+EOF
+
+when_run <<"EOF" "previous variable value in export, with word joining"
+export VAR=hello
+export VAR=" $VAR and goodbye"$VAR
+echo $VAR | cat -e
+EOF
+expecting <<EOF
+hello and goodbyehello$
+EOF
+
 finalize