1 files changed, 36 insertions, 0 deletions
diff --git a/libraries/base/tests/T12494.hs b/libraries/base/tests/T12494.hs
new file mode 100644
index 0000000000..544f5ed908
--- /dev/null
+++ b/libraries/base/tests/T12494.hs
@@ -0,0 +1,36 @@
+import System.Environment.Blank
+
+main = do
+  let envVar = "AN_ENVIRONMENT_VARIABLE"
+
+  valueBeforeSettingVariable <- getEnv envVar
+  print valueBeforeSettingVariable -- Nothing
+
+  valueWithDefaultBeforeSetting <- getEnvDefault envVar "DEFAULT"
+  print valueWithDefaultBeforeSetting -- "DEFAULT"
+
+  setEnv envVar "" False
+
+  valueAfterSettingVariable <- getEnv envVar
+  print valueAfterSettingVariable -- Just ""
+
+  valueWithDefaultAfterSetting <- getEnvDefault envVar "DEFAULT"
+  print valueWithDefaultAfterSetting -- ""
+
+  valueFromGetEnvironment <- lookup envVar <$> getEnvironment
+  print valueFromGetEnvironment -- Just ""
+
+  setEnv envVar "NO_OVERRIDE" False
+
+  valueAfterSettingWithExistingValueAndOverrideFalse <- getEnv envVar
+  print valueAfterSettingWithExistingValueAndOverrideFalse -- Just ""
+
+  setEnv envVar "OVERRIDE" True
+
+  valueAfterSettingWithExistingValueAndOverrideTrue <- getEnv envVar
+  print valueAfterSettingWithExistingValueAndOverrideTrue -- Just "OVERRIDE"
+
+  unsetEnv envVar
+
+  valueAfterUnsettingVariable <- getEnv envVar
+  print valueAfterUnsettingVariable -- Nothing