Add refute assertion

diff --git a/README.md b/README.md
index b341a8b..5636351 100644
--- a/README.md
+++ b/README.md

@@ -73,6 +73,30 @@
 ```
 
 
+### `refute`
+
+Fail if the given expression evaluates to true.
+
+***Note:*** *The expression must be a simple command. [Compound
+commands][bash-comp-cmd], such as `[[`, can be used only when executed
+with `bash -c`.*
+
+```bash
+@test 'refute()' {
+  rm -f '/var/log/test.log'
+  refute [ -e '/var/log/test.log' ]
+}
+```
+
+On failure, the successful expression is displayed.
+
+```
+-- assertion succeeded, but it was expected to fail --
+expression : [ -e /var/log/test.log ]
+--
+```
+
+
 ### `assert_equal`
 
 Fail if the two parameters, actual and expected value respectively, do

diff --git a/src/assert.bash b/src/assert.bash
index 7f87dc6..78b8416 100644
--- a/src/assert.bash
+++ b/src/assert.bash

@@ -71,6 +71,28 @@
   fi
 }
 
+# Fail and display the expression if it evaluates to true.
+#
+# NOTE: The expression must be a simple command. Compound commands, such
+#       as `[[', can be used only when executed with `bash -c'.
+#
+# Globals:
+#   none
+# Arguments:
+#   $1 - expression
+# Returns:
+#   0 - expression evaluates to FALSE
+#   1 - otherwise
+# Outputs:
+#   STDERR - details, on failure
+refute() {
+  if "$@"; then
+    batslib_print_kv_single 10 'expression' "$*" \
+      | batslib_decorate 'assertion succeeded, but it was expected to fail' \
+      | fail
+  fi
+}
+
 # Fail and display details if the expected and actual values do not
 # equal. Details include both values.
 #

diff --git a/test/50-assert-19-refute.bats b/test/50-assert-19-refute.bats
new file mode 100755
index 0000000..191dc73
--- /dev/null
+++ b/test/50-assert-19-refute.bats

@@ -0,0 +1,18 @@
+#!/usr/bin/env bats
+
+load test_helper
+
+@test 'refute() <expression>: returns 0 if <expression> evaluates to FALSE' {
+  run refute false
+  [ "$status" -eq 0 ]
+  [ "${#lines[@]}" -eq 0 ]
+}
+
+@test 'refute() <expression>: returns 1 and displays <expression> if it evaluates to TRUE' {
+  run refute true
+  [ "$status" -eq 1 ]
+  [ "${#lines[@]}" -eq 3 ]
+  [ "${lines[0]}" == '-- assertion succeeded, but it was expected to fail --' ]
+  [ "${lines[1]}" == 'expression : true' ]
+  [ "${lines[2]}" == '--' ]
+}