Added Jest snapshot test files as generated src (#3572)

lib/linguist/generated.rb

@@ -81,7 +81,8 @@ module Linguist
       generated_grammarkit? ||
       generated_roxygen2? ||
       generated_jison? ||
-      generated_yarn_lock?
+      generated_yarn_lock? ||
+      generated_jest_snapshot?
     end
 
     # Internal: Is the blob an Xcode file?
@@ -489,5 +490,15 @@ module Linguist
       return false unless lines.count > 0
       return lines[0].include?("# THIS IS AN AUTOGENERATED FILE")
     end
+
+    # Internal: Is this a Jest [snapshot test](https://facebook.github.io/jest/docs/snapshot-testing.html)
+    # file?
+    #
+    # Return true or false.
+    def generated_jest_snapshot?
+      return false unless extname == '.snap'
+      return false unless lines.count > 0
+      return lines[0].start_with?("// Jest Snapshot")
+    end
   end
 end

test/fixtures/Data/Jest.js.snap

@@ -0,0 +1,15 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`View renders correctly 1`] = `
+<View
+  style={
+    Object {
+      "alignItems": "center",
+      "flex": 1,
+      "margin": 40,
+      "paddingLeft": 10,
+      "paddingRight": 10,
+    }
+  }
+/>
+`;

test/test_generated.rb

@@ -79,9 +79,12 @@ class TestGenerated < Minitest::Test
     generated_fixture_loading_data("Data/sourcemap.v3.map")
     generated_fixture_loading_data("Data/sourcemap.v1.map")
 
-    # Yarn locfile
+    # Yarn lockfile
     generated_fixture_loading_data("Data/yarn.lock")
 
+    # Jest snapshot test
+    generated_fixture_loading_data("Data/Jest.js.snap")
+
     # Specflow
     generated_fixture_without_loading_data("Features/BindingCulture.feature.cs")