diff --git a/collects/tests/macro-debugger/all-tests.rkt b/collects/tests/macro-debugger/all-tests.rkt
index f742952..bba4768 100644
--- a/collects/tests/macro-debugger/all-tests.rkt
+++ b/collects/tests/macro-debugger/all-tests.rkt
@@ -1,17 +1,17 @@
 #lang scheme/base
 (require rackunit
          macro-debugger/model/debug
-         "gentest-framework.ss"
-         "gentests.ss"
-         "test-setup.ss"
-         "tests/syntax-basic.ss"
-         "tests/syntax-macros.ss"
-         "tests/syntax-modules.ss"
-         "tests/syntax-errors.ss"
-         "tests/hiding.ss"
-         "tests/regression.ss"
-         "tests/policy.ss"
-         ;;"tests/collects.ss"
+         "gentest-framework.rkt"
+         "gentests.rkt"
+         "test-setup.rkt"
+         "tests/syntax-basic.rkt"
+         "tests/syntax-macros.rkt"
+         "tests/syntax-modules.rkt"
+         "tests/syntax-errors.rkt"
+         "tests/hiding.rkt"
+         "tests/regression.rkt"
+         "tests/policy.rkt"
+         ;;"tests/collects.rkt"
          )
 (provide all-tests)
 
diff --git a/collects/tests/macro-debugger/gentests.rkt b/collects/tests/macro-debugger/gentests.rkt
index add1446..4561a7b 100644
--- a/collects/tests/macro-debugger/gentests.rkt
+++ b/collects/tests/macro-debugger/gentests.rkt
@@ -2,8 +2,8 @@
 (require rackunit)
 (require macro-debugger/model/debug
          macro-debugger/model/stx-util
-         "gentest-framework.ss"
-         "test-setup.ss")
+         "gentest-framework.rkt"
+         "test-setup.rkt")
 (provide mk-deriv-test
          mk-steps-test
          mk-hidden-deriv-test
diff --git a/collects/tests/macro-debugger/tests/hiding.rkt b/collects/tests/macro-debugger/tests/hiding.rkt
index 41780be..9033101 100644
--- a/collects/tests/macro-debugger/tests/hiding.rkt
+++ b/collects/tests/macro-debugger/tests/hiding.rkt
@@ -1,7 +1,7 @@
 #lang scheme/base
 (require rackunit)
 (require macro-debugger/model/debug
-         "../test-setup.ss")
+         "../test-setup.rkt")
 (provide specialized-hiding-tests)
 
 ;; == Macro hiding
diff --git a/collects/tests/macro-debugger/tests/policy.rkt b/collects/tests/macro-debugger/tests/policy.rkt
index 2abc459..27ef7ba 100644
--- a/collects/tests/macro-debugger/tests/policy.rkt
+++ b/collects/tests/macro-debugger/tests/policy.rkt
@@ -1,7 +1,7 @@
 #lang scheme/base
 (require rackunit)
 (require macro-debugger/model/debug
-         "../test-setup.ss")
+         "../test-setup.rkt")
 (provide policy-tests)
 
 (define ns (make-base-namespace))
diff --git a/collects/tests/macro-debugger/tests/regression.rkt b/collects/tests/macro-debugger/tests/regression.rkt
index 7e08837..8517fba 100644
--- a/collects/tests/macro-debugger/tests/regression.rkt
+++ b/collects/tests/macro-debugger/tests/regression.rkt
@@ -2,7 +2,7 @@
 (require rackunit)
 (require macro-debugger/model/debug
          macro-debugger/model/steps
-         "../test-setup.ss")
+         "../test-setup.rkt")
 (provide regression-tests)
 
 (define regression-tests
@@ -116,7 +116,7 @@
     (test-case "hiding: keeping lifts in sync"
       (let ([freshname (gensym)])
         (eval `(module ,freshname mzscheme
-                 (require (lib "contract.ss"))
+                 (require (lib "contract.rkt"))
                  (provide/contract [f (integer? . -> . integer?)]
                                    [c integer?])
                  (define (f x) (add1 x))
diff --git a/collects/tests/macro-debugger/tests/syntax-basic.rkt b/collects/tests/macro-debugger/tests/syntax-basic.rkt
index 2802799..5e01601 100644
--- a/collects/tests/macro-debugger/tests/syntax-basic.rkt
+++ b/collects/tests/macro-debugger/tests/syntax-basic.rkt
@@ -1,5 +1,5 @@
 #lang scheme/base
-(require "../gentest-framework.ss")
+(require "../gentest-framework.rkt")
 (provide proto:kernel-forms
          proto:kernel-contexts)
 
diff --git a/collects/tests/macro-debugger/tests/syntax-errors.rkt b/collects/tests/macro-debugger/tests/syntax-errors.rkt
index d51bfc3..a2c2deb 100644
--- a/collects/tests/macro-debugger/tests/syntax-errors.rkt
+++ b/collects/tests/macro-debugger/tests/syntax-errors.rkt
@@ -1,6 +1,5 @@
-
 #lang scheme/base
-(require "../gentest-framework.ss")
+(require "../gentest-framework.rkt")
 (provide proto:errors)
 
 (define-tests proto:errors "Bad syntax"
diff --git a/collects/tests/macro-debugger/tests/syntax-macros.rkt b/collects/tests/macro-debugger/tests/syntax-macros.rkt
index 8837463..9759962 100644
--- a/collects/tests/macro-debugger/tests/syntax-macros.rkt
+++ b/collects/tests/macro-debugger/tests/syntax-macros.rkt
@@ -1,6 +1,5 @@
-
 #lang scheme/base
-(require "../gentest-framework.ss")
+(require "../gentest-framework.rkt")
 (provide proto:macros)
 
 (define-tests proto:macros "Macros"
diff --git a/collects/tests/macro-debugger/tests/syntax-modules.rkt b/collects/tests/macro-debugger/tests/syntax-modules.rkt
index b4db2d1..3297fe2 100644
--- a/collects/tests/macro-debugger/tests/syntax-modules.rkt
+++ b/collects/tests/macro-debugger/tests/syntax-modules.rkt
@@ -1,6 +1,5 @@
-
 #lang scheme/base
-(require "../gentest-framework.ss")
+(require "../gentest-framework.rkt")
 (provide proto:modules)
 
 (define-syntax-rule (testM form . clauses)
@@ -327,9 +326,9 @@
           (P? (make-P P-x P-y))))
   (test "module with match"
         (module m mzscheme
-          (require (lib "match.ss"))
+          (require (lib "match.rkt"))
           (match '4 [n (add1 n)])))
   (test "module with match before require"
         (module m mzscheme
           (match '4 [n (add1 n)])
-          (require (lib "match.ss")))))
+          (require (lib "match.rkt")))))