n-api,test: add int64 bounds tests

Added some simple tests to verify that the int64 API is correctly
handling numbers greater than 32-bits. This is a basic test, but
verifies that an implementer hasn't truncated back to 32-bits.

Refs: nodejs/node-chakracore#496

PR-URL: nodejs#19309
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Gabriel Schulhof <gabriel.schulhof@intel.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

test/addons-napi/test_number/test.js

@@ -45,3 +45,10 @@ assert.strictEqual(1, test_number.TestInt32Truncation(4294967297));
 assert.strictEqual(0, test_number.TestInt32Truncation(4294967296));
 assert.strictEqual(-1, test_number.TestInt32Truncation(4294967295));
 assert.strictEqual(3, test_number.TestInt32Truncation(4294967296 * 5 + 3));
+
+// validate that the boundaries of safe integer can be passed through
+// successfully
+assert.strictEqual(Number.MAX_SAFE_INTEGER,
+                   test_number.TestInt64Truncation(Number.MAX_SAFE_INTEGER));
+assert.strictEqual(Number.MIN_SAFE_INTEGER,
+                   test_number.TestInt64Truncation(Number.MIN_SAFE_INTEGER));

test/addons-napi/test_number/test_number.c

@@ -45,10 +45,33 @@ napi_value TestInt32Truncation(napi_env env, napi_callback_info info) {
   return output;
 }
 
+napi_value TestInt64Truncation(napi_env env, napi_callback_info info) {
+  size_t argc = 1;
+  napi_value args[1];
+  NAPI_CALL(env, napi_get_cb_info(env, info, &argc, args, NULL, NULL));
+
+  NAPI_ASSERT(env, argc >= 1, "Wrong number of arguments");
+
+  napi_valuetype valuetype0;
+  NAPI_CALL(env, napi_typeof(env, args[0], &valuetype0));
+
+  NAPI_ASSERT(env, valuetype0 == napi_number,
+      "Wrong type of arguments. Expects a number as first argument.");
+
+  int64_t input;
+  NAPI_CALL(env, napi_get_value_int64(env, args[0], &input));
+
+  napi_value output;
+  NAPI_CALL(env, napi_create_int64(env, input, &output));
+
+  return output;
+}
+
 napi_value Init(napi_env env, napi_value exports) {
   napi_property_descriptor descriptors[] = {
     DECLARE_NAPI_PROPERTY("Test", Test),
     DECLARE_NAPI_PROPERTY("TestInt32Truncation", TestInt32Truncation),
+    DECLARE_NAPI_PROPERTY("TestInt64Truncation", TestInt64Truncation),
   };
 
   NAPI_CALL(env, napi_define_properties(