Minor addition to R unit tests

R-package/tests/testthat/test_poisson_regression.R

@@ -1,6 +1,7 @@
 context('Test poisson regression model')
 
 require(xgboost)
+set.seed(1994)
 
 test_that("poisson regression works", {
   data(mtcars)
@@ -9,5 +10,5 @@ test_that("poisson regression works", {
   expect_equal(class(bst), "xgb.Booster")
   pred <- predict(bst,as.matrix(mtcars[, -11]))
   expect_equal(length(pred), 32)
-  sqrt(mean( (pred - mtcars[,11]) ^ 2))
-})
+  expect_equal(sqrt(mean( (pred - mtcars[,11]) ^ 2)), 1.16, tolerance = 0.01)
+})