start on fake memory

get index checks on the array access of parfait

test/risc/test_fake_memory.rb

@@ -0,0 +1,50 @@
+require_relative "../helper"
+
+module Risc
+  class TestFakeMemory < MiniTest::Test
+    def setup
+      @fake = FakeMemory.new(2,16)
+    end
+    def test_init
+      assert @fake
+    end
+    def test_size
+      assert_equal 16 , @fake.size
+    end
+    def test_not_instantiates
+      assert_raises {FakeMemory.new(1,7)}
+    end
+    def test_access_fail_big
+      assert_raises {@fake.set(20 , 12)}
+    end
+    def test_access_fail_small
+      assert_raises {@fake.set(1 , 12)}
+    end
+    def test_access_fail_minus
+      assert_raises {@fake.set(-1 , 12)}
+    end
+    def test_set
+      assert_equal 12 ,  @fake.set(2 , 12)
+    end
+    def test_set_arr
+      assert_equal 12 ,  @fake[2] = 12
+    end
+    def test_get_no_init
+      assert_nil @fake.get(2)
+    end
+    def test_get_arr
+      assert_nil @fake[2]
+    end
+    def test_get_set
+      @fake[2] = 12
+      assert_equal 12 , @fake[2]
+    end
+    def test_set_all
+      (2...16).each{ |i| @fake[i] = i * 2}
+      assert_equal 4 , @fake[2]
+      assert_equal 30 , @fake[15]
+      assert_equal 16 , @fake.size
+    end
+
+  end
+end