Make it work with mocks and stubs

load.bash

diff --git a/load.bash b/load.bash
index 0727aeb..62c4622 100644
--- a/load.bash
+++ b/load.bash
@@ -1,3 +1,8 @@
+# Preserve path at the time this file was sourced
+# This prevents using of user-defined mocks/stubs that modify the PATH
+
+_BATSLIB_PATH="$PATH"
+
 source "$(dirname "${BASH_SOURCE[0]}")/src/output.bash"
 source "$(dirname "${BASH_SOURCE[0]}")/src/error.bash"
 source "$(dirname "${BASH_SOURCE[0]}")/src/lang.bash"

src/output.bash

diff --git a/src/output.bash b/src/output.bash
index c6cf6a6..6d260b1 100644
--- a/src/output.bash
+++ b/src/output.bash
@@ -38,7 +38,7 @@
   { if (( $# > 0 )); then
       echo "$@"
     else
-      cat -
+      ( PATH="$_BATSLIB_PATH"; command cat -; )
     fi
   } >&2
 }
@@ -273,7 +273,7 @@
 batslib_decorate() {
   echo
   echo "-- $1 --"
-  cat -
+  ( PATH="$_BATSLIB_PATH"; command cat -; )
   echo '--'
   echo
 }

test/50-output-10-batslib_err.bats

diff --git a/test/50-output-10-batslib_err.bats b/test/50-output-10-batslib_err.bats
index 8c27fd1..89b9db1 100755
--- a/test/50-output-10-batslib_err.bats
+++ b/test/50-output-10-batslib_err.bats
@@ -14,3 +14,30 @@
   [ "$status" -eq 0 ]
   [ "$output" == 'm1 m2' ]
 }
+
+@test 'batslib_err() works with modified path' {
+  export PATH="$BATS_TEST_DIRNAME:$PATH"
+  echo 'm1 m2' | {
+    # Verify stub
+    run which cat
+    [ "$status" -eq 0 ]
+    [ "$output" = "$BATS_TEST_DIRNAME/cat" ]
+    # Should still work
+    run batslib_err
+    [ "$status" -eq 0 ]
+    [ "$output" == 'm1 m2' ]
+  }
+}
+
+@test 'batslib_err() works with mock function' {
+  echo 'm1 m2' | {
+    function cat {
+      echo "Mocked cat"
+    }
+    [ "$(cat)" = "Mocked cat" ]
+    # Should still work
+    run batslib_err
+    [ "$status" -eq 0 ]
+    [ "$output" == 'm1 m2' ]
+  }
+}

test/50-output-19-batslib_decorate.bats

diff --git a/test/50-output-19-batslib_decorate.bats b/test/50-output-19-batslib_decorate.bats
index 02d55ad..a4d4fcb 100755
--- a/test/50-output-19-batslib_decorate.bats
+++ b/test/50-output-19-batslib_decorate.bats
@@ -11,3 +11,36 @@
   [ "${lines[1]}" == 'body' ]
   [ "${lines[2]}" == '--' ]
 }
+
+@test 'batslib_decorate() works with modified path' {
+  export PATH="$BATS_TEST_DIRNAME:$PATH"
+  echo body | {
+    # Verify stub
+    run which cat
+    [ "$status" -eq 0 ]
+    [ "$output" = "$BATS_TEST_DIRNAME/cat" ]
+    # Should still work
+    run batslib_decorate 'title'
+    [ "$status" -eq 0 ]
+    [ "${#lines[@]}" -eq 3 ]
+    [ "${lines[0]}" == '-- title --' ]
+    [ "${lines[1]}" == 'body' ]
+    [ "${lines[2]}" == '--' ]
+  }
+}
+
+@test 'batslib_decorate() works with mock function' {
+  echo body | {
+    function cat {
+      echo "Mocked cat"
+    }
+    [ "$(cat)" = "Mocked cat" ]
+    # Should still work
+    run batslib_decorate 'title'
+    [ "$status" -eq 0 ]
+    [ "${#lines[@]}" -eq 3 ]
+    [ "${lines[0]}" == '-- title --' ]
+    [ "${lines[1]}" == 'body' ]
+    [ "${lines[2]}" == '--' ]
+  }
+}

test/cat

diff --git a/test/cat b/test/cat
new file mode 100755
index 0000000..c45d58f
--- /dev/null
+++ b/test/cat
@@ -0,0 +1 @@
+# Dummy file stubbing a stub/mock