Add support for arbitrary Time objects

README.md

@@ -117,6 +117,7 @@ The following types are provided by Minitest-Proptest:
   * `Char` - any single character 0x00-0xff
   * `ASCIIChar` - any character 0x00-0x7f
   * `String` - arbitrary length string of `Char`s
+* `Time` - any time between 1901-12-13 20:45:52 and 2038-01-19 03:14:07 UTC
 * `Bool`
 * Polymorphic types
   * `Array a` - array of arbitrary length of another type

lib/minitest/proptest/gen.rb

@@ -451,6 +451,15 @@ def for(*classes)
       end.with_score_function do |_|
         1
       end
+
+      generator_for(Time) do
+        r = sized(0xffffffff)
+        Time.at((r & 0x80000000).zero? ? r : -((r ^ 0x7fffffff) - 0x7fffffff))
+      end.with_shrink_function do |t|
+        integral_shrink.call(t.to_i).map(&Time.method(:at))
+      end.with_score_function do |t|
+        t.to_i.abs
+      end
     end
   end
 end

test/property_test.rb

@@ -326,6 +326,22 @@ def test_shrink_bool
     end
   end
 
+  def test_shrink_time
+    gen = ::Minitest::Proptest::Gen.new(Random.new).for(Time)
+    property do
+      t = arbitrary Time
+      g = gen.force(t)
+      candidates = g.shrink_candidates
+
+      candidates.all? do |score, x|
+        score == x.to_i.abs &&
+          x.to_i <= 0x7fffffff &&
+          x.to_i >= -0x80000000 &&
+          ( t.to_i < 0 ? x.to_i <= 1 : x.to_i >= -1 )
+      end
+    end
+  end
+
   def test_where
     property do
       n = arbitrary Int32