1 files changed, 14 insertions, 0 deletions
diff --git a/hadrian/src/Rules/Selftest.hs b/hadrian/src/Rules/Selftest.hs
index 68aa6e3889..b931f85ef6 100644
--- a/hadrian/src/Rules/Selftest.hs
+++ b/hadrian/src/Rules/Selftest.hs
@@ -13,6 +13,8 @@ import Settings
 import Target
 import Utilities
 
+import qualified System.FilePath.Posix as Posix ((</>))
+
 instance Arbitrary Way where
     arbitrary = wayFromUnits <$> arbitrary
 
@@ -31,6 +33,7 @@ selftestRules =
         testLookupAll
         testModuleName
         testPackages
+        testPaths
         testWay
 
 testBuilder :: Action ()
@@ -111,3 +114,14 @@ testWay :: Action ()
 testWay = do
     putBuild "==== Read Way, Show Way"
     test $ \(x :: Way) -> read (show x) == x
+
+testPaths :: Action ()
+testPaths = do
+    putBuild "==== Absolute, Relative Path Concatenation"
+    test $ forAll paths $ \(path1, path2) ->
+      path1 -/- path2 == path1 Posix.</> path2
+  where
+    paths = (,) <$> path <*> path
+    path = frequency [(1, relativePath), (1, absolutePath)]
+    relativePath = intercalate "/" <$> listOf1 (elements ["a"])
+    absolutePath = ('/':) <$> relativePath