1 files changed, 91 insertions, 0 deletions
diff --git a/test/prism/test_helper.rb b/test/prism/test_helper.rb
new file mode 100644
index 0000000000..086b73dd56
--- /dev/null
+++ b/test/prism/test_helper.rb
@@ -0,0 +1,91 @@
+# frozen_string_literal: true
+
+require "yarp"
+require "ripper"
+require "pp"
+require "test/unit"
+require "tempfile"
+
+puts "Using YARP backend: #{YARP::BACKEND}" if ENV["YARP_FFI_BACKEND"]
+
+# It is useful to have a diff even if the strings to compare are big
+# However, ruby/ruby does not have a version of Test::Unit with access to
+# max_diff_target_string_size
+if defined?(Test::Unit::Assertions::AssertionMessage)
+  Test::Unit::Assertions::AssertionMessage.max_diff_target_string_size = 5000
+end
+
+module YARP
+  class TestCase < ::Test::Unit::TestCase
+    private
+
+    def assert_raises(*args, &block)
+      raise "Use assert_raise instead"
+    end
+
+    def assert_equal_nodes(expected, actual, compare_location: true, parent: nil)
+      assert_equal expected.class, actual.class
+
+      case expected
+      when Array
+        assert_equal(
+          expected.size,
+          actual.size,
+          -> { "Arrays were different sizes. Parent: #{parent.pretty_inspect}" }
+        )
+
+        expected.zip(actual).each do |(expected_element, actual_element)|
+          assert_equal_nodes(
+            expected_element,
+            actual_element,
+            compare_location: compare_location,
+            parent: actual
+          )
+        end
+      when SourceFileNode
+        deconstructed_expected = expected.deconstruct_keys(nil)
+        deconstructed_actual = actual.deconstruct_keys(nil)
+        assert_equal deconstructed_expected.keys, deconstructed_actual.keys
+
+        # Filepaths can be different if test suites were run on different
+        # machines. We accommodate for this by comparing the basenames, and not
+        # the absolute filepaths.
+        assert_equal deconstructed_expected.except(:filepath), deconstructed_actual.except(:filepath)
+        assert_equal File.basename(deconstructed_expected[:filepath]), File.basename(deconstructed_actual[:filepath])
+      when Node
+        deconstructed_expected = expected.deconstruct_keys(nil)
+        deconstructed_actual = actual.deconstruct_keys(nil)
+        assert_equal deconstructed_expected.keys, deconstructed_actual.keys
+
+        deconstructed_expected.each_key do |key|
+          assert_equal_nodes(
+            deconstructed_expected[key],
+            deconstructed_actual[key],
+            compare_location: compare_location,
+            parent: actual
+          )
+        end
+      when Location
+        assert_operator actual.start_offset, :<=, actual.end_offset, -> {
+          "start_offset > end_offset for #{actual.inspect}, parent is #{parent.pretty_inspect}"
+        }
+
+        if compare_location
+          assert_equal(
+            expected.start_offset,
+            actual.start_offset,
+            -> { "Start locations were different. Parent: #{parent.pretty_inspect}" }
+          )
+
+          assert_equal(
+            expected.end_offset,
+            actual.end_offset,
+            -> { "End locations were different. Parent: #{parent.pretty_inspect}" }
+          )
+        end
+      else
+        assert_equal expected, actual
+      end
+    end
+  end
+end