diff --git a/R/github-functions.R b/R/github-functions.R
index 0364eed..99fc0a5 100644
--- a/R/github-functions.R
+++ b/R/github-functions.R
@@ -19,10 +19,12 @@ getPkgVersFromFile <- function(file) {
     file <- sapply(strsplit(file, "\\.tgz"), "[[", 1)
     pkg  <- sapply(strsplit(file, "_"), "[[", 1)
     vers <- sapply(strsplit(file, "_"), "[[", 2)
-    df <- data.frame(package = pkg, version = vers, stringsAsFactors = FALSE)
-    df[order(df$package),]
+    df <- data.frame(package = pkg, version = vers, stringsAsFactors = FALSE, row.names = NULL)
+    df <- df[order(df$package),]
+    row.names(df) <- seq_len(nrow(df))
+    df
   } else {
-    NULL
+    data.frame(package = character(0), version = character(0))
   }
 }
 
diff --git a/tests/testthat/mock_data/pdb.rds b/tests/testthat/mock_data/pdb.rds
new file mode 100644
index 0000000..91331cc
Binary files /dev/null and b/tests/testthat/mock_data/pdb.rds differ
diff --git a/tests/testthat/test-1-github-functions.R b/tests/testthat/test-1-github-functions.R
new file mode 100644
index 0000000..e34854f
--- /dev/null
+++ b/tests/testthat/test-1-github-functions.R
@@ -0,0 +1,46 @@
+if (interactive()) library(testthat)
+
+# Copyright (c) Andrie de Vries 2018
+
+context("github-functions")
+
+test_that("package file extension is computed correctly", {
+  expect_equal(pkgFileExt("source"), ".tar.gz")
+  expect_equal(pkgFileExt("win.binary"), ".zip")
+  expect_equal(pkgFileExt("mac.binary"), ".tgz")
+  expect_error(pkgFileExt("nonsense"))
+})
+
+test_that("package verson is extracted correctly", {
+  ff <- c(
+    "KernSmooth_2.23-15.tar.gz",
+    "MASS_7.3-47.tar.gz",
+    "Matrix_1.2-12.tar.gz",
+    "boot_1.3-20.tar.gz"
+  )
+  expect_equal(
+    getPkgVersFromFile(ff),
+    data.frame(
+      package = c("boot", "KernSmooth", "MASS", "Matrix"),
+      version = c("1.3-20", "2.23-15", "7.3-47", "1.2-12"),
+      stringsAsFactors = FALSE,
+      row.names = NULL
+    )
+  )
+  
+  expect_equal(
+    getPkgVersFromFile("nonsense"),
+    data.frame(package = character(0), version = character(0))
+    )
+  
+})
+
+test_that("readDescription reads file", {
+  sf <- system.file("DESCRIPTION", package = "miniCRAN")
+  desc <- readDescription(sf)
+  
+  expect_is(desc, "list")
+  expect_true(
+    all(c("Imports", "Suggests", "Package") %in% names(desc))
+  )
+})
diff --git a/tests/testthat/test-6-getCranDescription.R b/tests/testthat/test-6-getCranDescription.R
index 7e5606c..3dd0bc2 100644
--- a/tests/testthat/test-6-getCranDescription.R
+++ b/tests/testthat/test-6-getCranDescription.R
@@ -4,6 +4,10 @@ context("get CRAN description")
 test_that("can read CRAN description", {
 
   skip_on_cran()
+  mockery::stub(getCranDescription, 
+                what = "tools::CRAN_package_db",
+                function(...) readRDS("mock_data/pdb.rds")
+                )
   p <- getCranDescription("miniCRAN", repos = c(CRAN = getOption("minicran.mran")))
   expect_is(p, "data.frame")
   expect_equal(p$Package[1], "miniCRAN")