diff --git a/spec/support/matchers/flash_message_matchers.rb b/spec/support/matchers/flash_message_matchers.rb
new file mode 100644
index 0000000000..b781fc1811
--- /dev/null
+++ b/spec/support/matchers/flash_message_matchers.rb
@@ -0,0 +1,31 @@
+RSpec::Matchers.define :have_flash_message do |message|
+  match do |node|
+    @message, @node = message, node
+
+    # Ignore leading and trailing whitespace. Later versions of Capybara have :exact_text option.
+    # The :exact option is not supported in has_selector?.
+    message_substring_regex = substring_match_regex(message)
+    node.has_selector?(".flash", text: message_substring_regex, visible: false)
+  end
+
+  failure_message do |actual|
+    "expected to find flash message ##{@message}"
+  end
+
+  match_when_negated do |node|
+    @message, @node = message, node
+
+    # Ignore leading and trailing whitespace. Later versions of Capybara have :exact_text option.
+    # The :exact option is not supported in has_selector?.
+    message_substring_regex = substring_match_regex(message)
+    node.has_no_selector?(".flash", text: message_substring_regex, visible: false)
+  end
+
+  failure_message_when_negated do |actual|
+    "expected not to find flash message ##{@message}"
+  end
+
+  def substring_match_regex(text)
+    /\A\s*#{Regexp.escape(text)}\s*\Z/
+  end
+end