diff --git a/pathtools/fs.go b/pathtools/fs.go
index b45c4a5..21754d0 100644
--- a/pathtools/fs.go
+++ b/pathtools/fs.go
@@ -131,6 +131,13 @@ func NewOsFs(path string) FileSystem {
 	return &osFs{srcDir: path}
 }
 
+func (fs *osFs) toAbs(path string) string {
+	if filepath.IsAbs(path) {
+		return path
+	}
+	return filepath.Join(fs.srcDir, path)
+}
+
 func (fs *osFs) removeSrcDirPrefix(path string) string {
 	if fs.srcDir == "" {
 		return path
@@ -157,11 +164,11 @@ func (fs *osFs) removeSrcDirPrefixes(paths []string) []string {
 }
 
 func (fs *osFs) Open(name string) (ReaderAtSeekerCloser, error) {
-	return os.Open(filepath.Join(fs.srcDir, name))
+	return os.Open(fs.toAbs(name))
 }
 
 func (fs *osFs) Exists(name string) (bool, bool, error) {
-	stat, err := os.Stat(filepath.Join(fs.srcDir, name))
+	stat, err := os.Stat(fs.toAbs(name))
 	if err == nil {
 		return true, stat.IsDir(), nil
 	} else if os.IsNotExist(err) {
@@ -172,7 +179,7 @@ func (fs *osFs) Exists(name string) (bool, bool, error) {
 }
 
 func (fs *osFs) IsDir(name string) (bool, error) {
-	info, err := os.Stat(filepath.Join(fs.srcDir, name))
+	info, err := os.Stat(fs.toAbs(name))
 	if err != nil {
 		return false, err
 	}
@@ -180,7 +187,7 @@ func (fs *osFs) IsDir(name string) (bool, error) {
 }
 
 func (fs *osFs) IsSymlink(name string) (bool, error) {
-	if info, err := os.Lstat(filepath.Join(fs.srcDir, name)); err != nil {
+	if info, err := os.Lstat(fs.toAbs(name)); err != nil {
 		return false, err
 	} else {
 		return info.Mode()&os.ModeSymlink != 0, nil
@@ -192,17 +199,17 @@ func (fs *osFs) Glob(pattern string, excludes []string, follow ShouldFollowSymli
 }
 
 func (fs *osFs) glob(pattern string) ([]string, error) {
-	paths, err := filepath.Glob(filepath.Join(fs.srcDir, pattern))
+	paths, err := filepath.Glob(fs.toAbs(pattern))
 	fs.removeSrcDirPrefixes(paths)
 	return paths, err
 }
 
 func (fs *osFs) Lstat(path string) (stats os.FileInfo, err error) {
-	return os.Lstat(filepath.Join(fs.srcDir, path))
+	return os.Lstat(fs.toAbs(path))
 }
 
 func (fs *osFs) Stat(path string) (stats os.FileInfo, err error) {
-	return os.Stat(filepath.Join(fs.srcDir, path))
+	return os.Stat(fs.toAbs(path))
 }
 
 // Returns a list of all directories under dir
@@ -211,7 +218,7 @@ func (fs *osFs) ListDirsRecursive(name string, follow ShouldFollowSymlinks) (dir
 }
 
 func (fs *osFs) ReadDirNames(name string) ([]string, error) {
-	dir, err := os.Open(filepath.Join(fs.srcDir, name))
+	dir, err := os.Open(fs.toAbs(name))
 	if err != nil {
 		return nil, err
 	}
@@ -227,7 +234,7 @@ func (fs *osFs) ReadDirNames(name string) ([]string, error) {
 }
 
 func (fs *osFs) Readlink(name string) (string, error) {
-	return os.Readlink(filepath.Join(fs.srcDir, name))
+	return os.Readlink(fs.toAbs(name))
 }
 
 type mockFs struct {
diff --git a/pathtools/fs_test.go b/pathtools/fs_test.go
index a9a7060..3b4d4d0 100644
--- a/pathtools/fs_test.go
+++ b/pathtools/fs_test.go
@@ -103,6 +103,42 @@ func TestMockFs_followSymlinks(t *testing.T) {
 	}
 }
 
+func runTestFs(t *testing.T, f func(t *testing.T, fs FileSystem, dir string)) {
+	mock := symlinkMockFs()
+	wd, _ := os.Getwd()
+	absTestDataDir := filepath.Join(wd, testdataDir)
+
+	run := func(t *testing.T, fs FileSystem) {
+		t.Run("relpath", func(t *testing.T) {
+			f(t, fs, "")
+		})
+		t.Run("abspath", func(t *testing.T) {
+			f(t, fs, absTestDataDir)
+		})
+	}
+
+	t.Run("mock", func(t *testing.T) {
+		f(t, mock, "")
+	})
+
+	t.Run("os", func(t *testing.T) {
+		os.Chdir(absTestDataDir)
+		defer os.Chdir(wd)
+		run(t, OsFs)
+	})
+
+	t.Run("os relative srcDir", func(t *testing.T) {
+		run(t, NewOsFs(testdataDir))
+	})
+
+	t.Run("os absolute srcDir", func(t *testing.T) {
+		os.Chdir("/")
+		defer os.Chdir(wd)
+		run(t, NewOsFs(filepath.Join(wd, testdataDir)))
+	})
+
+}
+
 func TestFs_IsDir(t *testing.T) {
 	testCases := []struct {
 		name  string
@@ -150,37 +186,16 @@ func TestFs_IsDir(t *testing.T) {
 		{"c/f/missing", false, syscall.ENOTDIR},
 	}
 
-	mock := symlinkMockFs()
-
-	run := func(t *testing.T, fs FileSystem) {
+	runTestFs(t, func(t *testing.T, fs FileSystem, dir string) {
 		for _, test := range testCases {
 			t.Run(test.name, func(t *testing.T) {
-				got, err := fs.IsDir(test.name)
+				got, err := fs.IsDir(filepath.Join(dir, test.name))
 				checkErr(t, test.err, err)
 				if got != test.isDir {
 					t.Errorf("want: %v, got %v", test.isDir, got)
 				}
 			})
 		}
-	}
-
-	t.Run("mock", func(t *testing.T) {
-		run(t, mock)
-	})
-
-	t.Run("os", func(t *testing.T) {
-		os.Chdir("testdata/dangling")
-		defer os.Chdir("../..")
-		run(t, OsFs)
-	})
-
-	t.Run("os relative srcDir", func(t *testing.T) {
-		run(t, NewOsFs(testdataDir))
-	})
-
-	t.Run("os absolute srcDir", func(t *testing.T) {
-		wd, _ := os.Getwd()
-		run(t, NewOsFs(filepath.Join(wd, testdataDir)))
 	})
 }
 
@@ -213,37 +228,20 @@ func TestFs_ListDirsRecursiveFollowSymlinks(t *testing.T) {
 		{"missing", nil, os.ErrNotExist},
 	}
 
-	mock := symlinkMockFs()
-
-	run := func(t *testing.T, fs FileSystem) {
+	runTestFs(t, func(t *testing.T, fs FileSystem, dir string) {
 		for _, test := range testCases {
 			t.Run(test.name, func(t *testing.T) {
-				got, err := fs.ListDirsRecursive(test.name, FollowSymlinks)
+				got, err := fs.ListDirsRecursive(filepath.Join(dir, test.name), FollowSymlinks)
 				checkErr(t, test.err, err)
-				if !reflect.DeepEqual(got, test.dirs) {
-					t.Errorf("want: %v, got %v", test.dirs, got)
+				want := append([]string(nil), test.dirs...)
+				for i := range want {
+					want[i] = filepath.Join(dir, want[i])
+				}
+				if !reflect.DeepEqual(got, want) {
+					t.Errorf("want: %v, got %v", want, got)
 				}
 			})
 		}
-	}
-
-	t.Run("mock", func(t *testing.T) {
-		run(t, mock)
-	})
-
-	t.Run("os", func(t *testing.T) {
-		os.Chdir("testdata/dangling")
-		defer os.Chdir("../..")
-		run(t, OsFs)
-	})
-
-	t.Run("os relative srcDir", func(t *testing.T) {
-		run(t, NewOsFs(testdataDir))
-	})
-
-	t.Run("os absolute srcDir", func(t *testing.T) {
-		wd, _ := os.Getwd()
-		run(t, NewOsFs(filepath.Join(wd, testdataDir)))
 	})
 }
 
@@ -276,37 +274,20 @@ func TestFs_ListDirsRecursiveDontFollowSymlinks(t *testing.T) {
 		{"missing", nil, os.ErrNotExist},
 	}
 
-	mock := symlinkMockFs()
-
-	run := func(t *testing.T, fs FileSystem) {
+	runTestFs(t, func(t *testing.T, fs FileSystem, dir string) {
 		for _, test := range testCases {
 			t.Run(test.name, func(t *testing.T) {
-				got, err := fs.ListDirsRecursive(test.name, DontFollowSymlinks)
+				got, err := fs.ListDirsRecursive(filepath.Join(dir, test.name), DontFollowSymlinks)
 				checkErr(t, test.err, err)
-				if !reflect.DeepEqual(got, test.dirs) {
-					t.Errorf("want: %v, got %v", test.dirs, got)
+				want := append([]string(nil), test.dirs...)
+				for i := range want {
+					want[i] = filepath.Join(dir, want[i])
+				}
+				if !reflect.DeepEqual(got, want) {
+					t.Errorf("want: %v, got %v", want, got)
 				}
 			})
 		}
-	}
-
-	t.Run("mock", func(t *testing.T) {
-		run(t, mock)
-	})
-
-	t.Run("os", func(t *testing.T) {
-		os.Chdir("testdata/dangling")
-		defer os.Chdir("../..")
-		run(t, OsFs)
-	})
-
-	t.Run("os relative srcDir", func(t *testing.T) {
-		run(t, NewOsFs(testdataDir))
-	})
-
-	t.Run("os absolute srcDir", func(t *testing.T) {
-		wd, _ := os.Getwd()
-		run(t, NewOsFs(filepath.Join(wd, testdataDir)))
 	})
 }
 
@@ -356,9 +337,7 @@ func TestFs_Readlink(t *testing.T) {
 		{"dangling/missing/missing", "", os.ErrNotExist},
 	}
 
-	mock := symlinkMockFs()
-
-	run := func(t *testing.T, fs FileSystem) {
+	runTestFs(t, func(t *testing.T, fs FileSystem, dir string) {
 		for _, test := range testCases {
 			t.Run(test.from, func(t *testing.T) {
 				got, err := fs.Readlink(test.from)
@@ -368,25 +347,6 @@ func TestFs_Readlink(t *testing.T) {
 				}
 			})
 		}
-	}
-
-	t.Run("mock", func(t *testing.T) {
-		run(t, mock)
-	})
-
-	t.Run("os", func(t *testing.T) {
-		os.Chdir("testdata/dangling")
-		defer os.Chdir("../..")
-		run(t, OsFs)
-	})
-
-	t.Run("os relative srcDir", func(t *testing.T) {
-		run(t, NewOsFs(testdataDir))
-	})
-
-	t.Run("os absolute srcDir", func(t *testing.T) {
-		wd, _ := os.Getwd()
-		run(t, NewOsFs(filepath.Join(wd, testdataDir)))
 	})
 }
 
@@ -438,12 +398,10 @@ func TestFs_Lstat(t *testing.T) {
 		{"dangling/missing/missing", 0, 0, os.ErrNotExist},
 	}
 
-	mock := symlinkMockFs()
-
-	run := func(t *testing.T, fs FileSystem) {
+	runTestFs(t, func(t *testing.T, fs FileSystem, dir string) {
 		for _, test := range testCases {
 			t.Run(test.name, func(t *testing.T) {
-				got, err := fs.Lstat(test.name)
+				got, err := fs.Lstat(filepath.Join(dir, test.name))
 				checkErr(t, test.err, err)
 				if err != nil {
 					return
@@ -457,25 +415,6 @@ func TestFs_Lstat(t *testing.T) {
 				}
 			})
 		}
-	}
-
-	t.Run("mock", func(t *testing.T) {
-		run(t, mock)
-	})
-
-	t.Run("os", func(t *testing.T) {
-		os.Chdir("testdata/dangling")
-		defer os.Chdir("../..")
-		run(t, OsFs)
-	})
-
-	t.Run("os relative srcDir", func(t *testing.T) {
-		run(t, NewOsFs(testdataDir))
-	})
-
-	t.Run("os absolute srcDir", func(t *testing.T) {
-		wd, _ := os.Getwd()
-		run(t, NewOsFs(filepath.Join(wd, testdataDir)))
 	})
 }
 
@@ -527,12 +466,10 @@ func TestFs_Stat(t *testing.T) {
 		{"dangling/missing/missing", 0, 0, os.ErrNotExist},
 	}
 
-	mock := symlinkMockFs()
-
-	run := func(t *testing.T, fs FileSystem) {
+	runTestFs(t, func(t *testing.T, fs FileSystem, dir string) {
 		for _, test := range testCases {
 			t.Run(test.name, func(t *testing.T) {
-				got, err := fs.Stat(test.name)
+				got, err := fs.Stat(filepath.Join(dir, test.name))
 				checkErr(t, test.err, err)
 				if err != nil {
 					return
@@ -546,25 +483,6 @@ func TestFs_Stat(t *testing.T) {
 				}
 			})
 		}
-	}
-
-	t.Run("mock", func(t *testing.T) {
-		run(t, mock)
-	})
-
-	t.Run("os", func(t *testing.T) {
-		os.Chdir("testdata/dangling")
-		defer os.Chdir("../..")
-		run(t, OsFs)
-	})
-
-	t.Run("os relative srcDir", func(t *testing.T) {
-		run(t, NewOsFs(testdataDir))
-	})
-
-	t.Run("os absolute srcDir", func(t *testing.T) {
-		wd, _ := os.Getwd()
-		run(t, NewOsFs(filepath.Join(wd, testdataDir)))
 	})
 }
 
@@ -606,9 +524,7 @@ func TestMockFs_glob(t *testing.T) {
 		{"missing", nil},
 	}
 
-	mock := symlinkMockFs()
-
-	run := func(t *testing.T, fs FileSystem) {
+	runTestFs(t, func(t *testing.T, fs FileSystem, dir string) {
 		for _, test := range testCases {
 			t.Run(test.pattern, func(t *testing.T) {
 				got, err := fs.glob(test.pattern)
@@ -620,25 +536,6 @@ func TestMockFs_glob(t *testing.T) {
 				}
 			})
 		}
-	}
-
-	t.Run("mock", func(t *testing.T) {
-		run(t, mock)
-	})
-
-	t.Run("os", func(t *testing.T) {
-		os.Chdir("testdata/dangling")
-		defer os.Chdir("../..")
-		run(t, OsFs)
-	})
-
-	t.Run("os relative srcDir", func(t *testing.T) {
-		run(t, NewOsFs(testdataDir))
-	})
-
-	t.Run("os absolute srcDir", func(t *testing.T) {
-		wd, _ := os.Getwd()
-		run(t, NewOsFs(filepath.Join(wd, testdataDir)))
 	})
 }