Add example code and test for R CMD check

R/hello.R

@@ -0,0 +1,18 @@
+# Hello, world!
+#
+# This is an example function named 'hello' 
+# which prints 'Hello, world!'.
+#
+# You can learn more about package authoring with RStudio at:
+#
+#   https://r-pkgs.org
+#
+# Some useful keyboard shortcuts for package authoring:
+#
+#   Install Package:           'Cmd + Shift + B'
+#   Check Package:             'Cmd + Shift + E'
+#   Test Package:              'Cmd + Shift + T'
+
+hello <- function() {
+  print("Hello, world!")
+}

tests/testthat.R

@@ -0,0 +1,12 @@
+# This file is part of the standard setup for testthat.
+# It is recommended that you do not modify it.
+#
+# Where should you do additional test configuration?
+# Learn more about the roles of various files in:
+# * https://r-pkgs.org/testing-design.html#sec-tests-files-overview
+# * https://testthat.r-lib.org/articles/special-files.html
+
+library(testthat)
+library(CRiSp)
+
+test_check("CRiSp")

tests/testthat/test-hello.R

@@ -0,0 +1,3 @@
+test_that("multiplication works", {
+  expect_equal(2 * 2, 4)
+})