diff --git a/README.md b/README.md
index 0193cab..3a26590 100644
--- a/README.md
+++ b/README.md
@@ -51,6 +51,8 @@ assert_eq "hello" "world"
 * `assert_ge` checks whether the first param is greator than or equal to the second one.
 * `assert_lt` checks whether the first param is less than the second one.
 * `assert_le` checks whether the first param is less than or equal to the second one.
+* `assert_file_exist` checks whether the first param is an existing regular file.
+* `assert_file_not_exist` checks whether the first param is not an existing regular file.
 
 ### How to write tests
 
diff --git a/assert.sh b/assert.sh
index 32e7da5..14b25fe 100755
--- a/assert.sh
+++ b/assert.sh
@@ -214,10 +214,15 @@ assert_contain() {
     return 0;
   fi
 
+ if [ -z "${haystack:+x}" ] && [ ! -z "${needle:+x}" ]; then
+    [ "${#msg}" -gt 0 ] && log_failure "'$haystack' doesn't contain '$needle' :: $msg" || true
+    return 1;
+  fi
+
   if [ -z "${haystack##*$needle*}" ]; then
     return 0
   else
-    [ "${#msg}" -gt 0 ] && log_failure "$haystack doesn't contain $needle :: $msg" || true
+    [ "${#msg}" -gt 0 ] && log_failure "'$haystack' doesn't contain '$needle' :: $msg" || true
     return 1
   fi
 }
@@ -231,6 +236,15 @@ assert_not_contain() {
     msg="$3"
   fi
 
+  if [ -z "${haystack:+x}" ] && [ -z "${needle:+x}" ]; then
+    [ "${#msg}" -gt 0 ] && log_failure "'$haystack' contains '$needle' :: $msg" || true
+    return 1;
+  fi
+
+  if [ -z "${haystack:+x}" ]; then
+    return 0;
+  fi
+
   if [ -z "${needle:+x}" ]; then
     return 0;
   fi
@@ -238,7 +252,7 @@ assert_not_contain() {
   if [ "${haystack##*$needle*}" ]; then
     return 0
   else
-    [ "${#msg}" -gt 0 ] && log_failure "$haystack contains $needle :: $msg" || true
+    [ "${#msg}" -gt 0 ] && log_failure "'$haystack' contains '$needle' :: $msg" || true
     return 1
   fi
 }
@@ -310,3 +324,35 @@ assert_le() {
     return 1
   fi
 }
+
+assert_file_exist() {
+    local first="$1"
+    local msg
+
+    if [ "$#" -ge 2 ]; then
+        msg="$2"
+    fi
+
+    if [[ -f  "$first" ]]; then
+      return 0
+    else
+      [ "${#msg}" -gt 0 ] && log_failure "$first ! exist :: $msg" || true
+      return 1
+    fi
+}
+
+assert_file_not_exist() {
+    local first="$1"
+    local msg
+
+    if [ "$#" -ge 2 ]; then
+        msg="$2"
+    fi
+
+    if [[ ! -f  "$first" ]]; then
+      return 0
+    else
+      [ "${#msg}" -gt 0 ] && log_failure "$first exists :: $msg" || true
+      return 1
+    fi
+}
diff --git a/test_assert.sh b/test_assert.sh
index eab0e30..862d84a 100755
--- a/test_assert.sh
+++ b/test_assert.sh
@@ -292,6 +292,27 @@ test_assert_contain() {
   else
     log_failure "assert_contain does not work"
   fi
+
+  assert_contain "" "needle"
+  if [ "$?" == 1 ]; then
+    log_success "assert_contain returns 1 if the haystack is an empty string"
+  else
+    log_failure "assert_contain does not work"
+  fi
+
+  assert_contain "haystack" ""
+  if [ "$?" == 0 ]; then
+    log_success "assert_contain returns 0 if the needle is an empty string"
+  else
+    log_failure "assert_contain does not work"
+  fi
+
+  assert_contain "" ""
+  if [ "$?" == 0 ]; then
+    log_success "assert_contain returns 0 if the haystack and needle are empty strings"
+  else
+    log_failure "assert_contain does not work"
+  fi
 }
 
 test_assert_not_contain() {
@@ -359,6 +380,28 @@ test_assert_not_contain() {
   else
     log_failure "assert_not_contain does not work"
   fi
+
+#  assert_not_contain haystack needle
+  assert_not_contain "" "needle"
+  if [ "$?" == 0 ]; then
+    log_success "assert_not_contain returns 0 if the haystack is an empty string"
+  else
+    log_failure "assert_not_contain does not work"
+  fi
+
+  assert_not_contain "haystack" ""
+  if [ "$?" == 0 ]; then
+    log_success "assert_not_contain returns 1 if the needle is an empty string"
+  else
+    log_failure "assert_not_contain does not work"
+  fi
+
+  assert_not_contain "" ""
+  if [ "$?" == 1 ]; then
+    log_success "assert_not_contain returns 1 if the haystack and needle are empty strings"
+  else
+    log_failure "assert_not_contain does not work"
+  fi
 }
 
 test_assert_gt() {
@@ -465,6 +508,77 @@ test_assert_le() {
   fi
 }
 
+test_assert_file_exist() {
+  log_header "Test :: assert_file_exist"
+
+  local tmp_existing_file="tmp_test_file"
+  local tmp_non_existent_fle="tmp_should_not_exist_file"
+  local tmp_existing_dir="tmp_test_dir"
+
+  # ci-before
+  echo "A test file" > "$tmp_existing_file"
+  mkdir "$tmp_existing_dir"
+
+  assert_file_exist "$tmp_existing_file"
+  if [ "$?" == 0 ]; then
+    log_success "assert_file_exist returns 0 if param is existing file"
+  else
+    log_failure "assert_file_exist does not work"
+  fi
+
+  assert_file_exist "$tmp_non_existent_fle"
+  if [ "$?" == 1 ]; then
+    log_success "assert_file_exist returns 1 if param is not existing path"
+  else
+    log_failure "assert_file_exist does not work"
+  fi
+
+  assert_file_exist "$tmp_existing_dir"
+  if [ "$?" == 1 ]; then
+    log_success "assert_file_exist returns 1 if param is a existing directory"
+  else
+    log_failure "assert_file_exist does not work"
+  fi
+
+  # ci-after
+  rm -rf "$tmp_existing_file" "$tmp_existing_dir"
+}
+
+test_assert_file_not_exist() {
+  log_header "Test :: assert_file_not_exist"
+
+  local tmp_existing_file="tmp_test_file"
+  local tmp_non_existent_fle="tmp_should_not_exist_file"
+  local tmp_existing_dir="tmp_test_dir"
+
+  # ci-before
+  echo "A test file" > "$tmp_existing_file"
+  mkdir "$tmp_existing_dir"
+
+  assert_file_not_exist "$tmp_non_existent_fle"
+  if [ "$?" == 0 ]; then
+    log_success "assert_file_not_exist returns 0 if param is non existing file"
+  else
+    log_failure "assert_file_not_exist does not work"
+  fi
+
+  assert_file_not_exist "$tmp_existing_dir"
+  if [ "$?" == 0 ]; then
+    log_success "assert_file_not_exist returns 1 if param is a existing directory"
+  else
+    log_failure "assert_file_not_exist does not work"
+  fi
+
+  assert_file_not_exist "$tmp_existing_file"
+  if [ "$?" == 1 ]; then
+    log_success "assert_file_not_exist returns 1 if param is a existing file"
+  else
+    log_failure "assert_file_not_exist does not work"
+  fi
+
+  # ci-after
+  rm -rf "$tmp_existing_file" "$tmp_existing_dir"
+}
 
 
 # test calls
@@ -483,4 +597,5 @@ test_assert_gt
 test_assert_ge
 test_assert_lt
 test_assert_le
-
+test_assert_file_exist
+test_assert_file_not_exist