diff --git a/content/code/tdd_sol.R b/content/code/tdd_sol.R
index d49c92c..98d3765 100644
--- a/content/code/tdd_sol.R
+++ b/content/code/tdd_sol.R
@@ -1 +1,40 @@
-WRITEME
\ No newline at end of file
+# define the function
+fizz_buzz <- function(number){
+  if(!number%%1==0 | number < 0) {
+     stop("non-integer or negative input not allowed!")
+  }
+  if(number%%3 == 0 & number%%5 == 0) {
+    return('FizzBuzz')
+  }
+  else if(number%%3 == 0) {
+    return('Fizz')
+  }
+  else if (number%%5 == 0){
+    return('Buzz')
+  }
+  else {
+    return(number)
+  }
+  
+}
+
+# apply it to the numbers 1 to 50
+for (number in 1:50) {
+  print(fizz_buzz(number))
+}
+
+
+library(testthat)
+
+test_that("Test FizzBuzz", {
+  expect_equal(fizz_buzz(1), 1)
+  expect_equal(fizz_buzz(2), 2)
+  expect_equal(fizz_buzz(3), 'Fizz')
+  expect_equal(fizz_buzz(4), 4)
+  expect_equal(fizz_buzz(5), 'Buzz')
+  expect_equal(fizz_buzz(15), 'FizzBuzz')  
+
+  expect_error(fizz_buzz(-1))
+  expect_error(fizz_buzz(1.5))
+  expect_error(fizz_buzz('rabbit'))    
+})