unit test to confirm no source dir modifications

tests/testthat.R

@@ -57,6 +57,11 @@ if(identical(Sys.getenv("NOT_CRAN"), "true")){
 
     }
 
+    # Record modifaction time of package directory to be checked at end of testing 
+    # in test-Z-test-no-source-modifcations.R
+    tmp_pkgnet_path <- file.path(Sys.getenv('PKGNET_TEST_LIB'), 'pkgnet')
+    Sys.setenv(PKGNET_LATEST_MOD = file.info(tmp_pkgnet_path)$mtime)
+
     # This withr statement should be redundant.
     # This is within a test environment in which .libpaths() has been altered to include PKGNET_TEST_LIB.
     # Yet, it appears to be necessary.

tests/testthat/test-Z-test-no-source-modifcations.R

@@ -0,0 +1,17 @@
+# Inditended to be run last, this is to confirm that no files 
+# within the package directory are modified during the normal 
+# operation of pkgnet during these tests.  This includes the 
+# creation and deletion of temp files for rendering. 
+
+test_that('No modificatoin to pkgnet directory during testing',{
+    startModTime <- Sys.getenv('PKGNET_LATEST_MOD')
+
+    tmp_pkgnet_path <- file.path(Sys.getenv('PKGNET_TEST_LIB'), 'pkgnet')
+    currentModTime <- file.info(tmp_pkgnet_path)$mtime
+
+    expect_equal(object = currentModTime
+                 , expected = startModTime
+                 , info = "The source directory was modified during the execution of tests."
+                 )
+
+})