diff --git a/.gitignore b/.gitignore
index 4544b4f..47e6166 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,4 +1,6 @@
 *~
+*.swp
+*.swo
 *.o
 *.so
 *.a
diff --git a/functional-tests/binary-format.scm b/functional-tests/binary-format.scm
new file mode 100644
index 0000000..95c18e0
--- /dev/null
+++ b/functional-tests/binary-format.scm
@@ -0,0 +1,41 @@
+(library
+  (binary-format)
+  (export binary-format)
+  (import (rnrs))
+
+  (define-syntax unpack-type
+    (syntax-rules (le32 le64 bytes)
+      ((_ bv offset le32)
+       (bytevector-u32-ref bv offset (endianness little)))
+
+      ((_ bv offset le64)
+       (bytevector-u64-ref bv offset (endianness little)))
+
+      ((_ bv offset (bytes count))
+       (let ((copy (make-bytevector count)))
+        (bytevector-copy! bv offset copy 0 count)
+        copy))))
+
+  (define (size-type t)
+    (syntax-case t (le32 le64 bytes)
+                 (le32 #'4)
+                 (le64 #'8)
+                 ((bytes count) #'count)))
+
+  ;;; FIXME: (bytes <count>) has to use a literal rather than a symbol.
+  (define-syntax binary-format
+    (lambda (x)
+      (syntax-case x ()
+                   ((_ (name pack-name unpack-name) (field type) ...)
+                    (with-syntax ((((t o) ...)
+                                   (let f ((acc 0) (types #'(type ...)))
+                                    (if (null? types)
+                                        '()
+                                        (cons (list (car types) acc)
+                                              (f (+ (syntax->datum (size-type (car types))) acc) (cdr types)))))))
+                                 #`(begin
+                                     (define-record-type name (fields field ...))
+
+                                     (define (unpack-name bv offset)
+                                       ((record-constructor (record-type-descriptor name))
+                                        (unpack-type bv (+ offset o) t) ...)))))))))
diff --git a/functional-tests/block-io.scm b/functional-tests/block-io.scm
new file mode 100644
index 0000000..dc873a2
--- /dev/null
+++ b/functional-tests/block-io.scm
@@ -0,0 +1,53 @@
+(library
+  (block-io)
+  (export metadata-block-size
+          open-metadata
+          with-metadata
+          read-block)
+  (import (rnrs)
+          (fmt fmt))
+
+  ;;;---------------------------------------------------
+  ;;; TODO:
+  ;;; - implement a little block cache.
+  ;;; - writes
+  ;;; - zero blocks
+  ;;; - prefetching
+  ;;;---------------------------------------------------
+
+  (define metadata-block-size 4096)
+
+  (define (open-metadata path)
+    (open-file-input-port path (file-options) (buffer-mode none)))
+
+  (define-syntax with-metadata
+    (syntax-rules ()
+      ((_ (port path) body ...) (let ((port (open-metadata path)))
+                                 (dynamic-wind
+                                   (lambda () #f)
+                                   (lambda () body ...)
+                                   (lambda () (close-port port)))))))
+
+  ;; FIXME: return our own condition?
+  (define (io-error msg)
+    (raise (condition
+             (make-error)
+             (make-message-condition msg))))
+
+  ;;; Returns a boolean indicating success
+  (define (read-exact! port offset len bv start)
+    (set-port-position! port offset)
+    (let ((nr (get-bytevector-n! port bv start len)))
+     (and (not (eof-object? nr))
+          (= len nr))))
+
+  ;;; Returns a 4k bytevector or #f
+  (define (read-exact port offset len)
+    (let ((bv (make-bytevector len)))
+     (if (read-exact! port offset len bv 0) bv #f)))
+
+  (define (read-block port b)
+    (or (read-exact port (* b metadata-block-size) metadata-block-size)
+        (io-error (fmt #f (dsp "Unable to read metadata block: ") (num b))))))
+
+
diff --git a/functional-tests/check-superblock.scm b/functional-tests/check-superblock.scm
index 3129d1d..e3cccb8 100644
--- a/functional-tests/check-superblock.scm
+++ b/functional-tests/check-superblock.scm
@@ -1,4 +1,5 @@
 (import
+  (block-io)
   (fmt fmt)
   (matchable))
 
@@ -10,115 +11,11 @@
 (define (current-metadata)
   "./metadata.bin")
 
-(define metadata-block-size 4096)
 (define superblock-magic 27022010)
 (define superblock-salt 160774)
 (define uuid-size 16)
 (define space-map-root-size 128)
 
-;;;;---------------------------------------------------
-;;;; Metadata IO
-;;;;---------------------------------------------------
-
-(define (open-metadata path)
-  (open-file-input-port path (file-options) (buffer-mode none)))
-
-(define-syntax with-metadata
-  (syntax-rules ()
-    ((_ (port path) body ...) (let ((port (open-metadata path)))
-                                (dynamic-wind
-                                  (lambda () #f)
-                                  (lambda () body ...)
-                                  (lambda () (close-port port)))))))
-
-;; FIXME: return our own condition?
-(define (io-error msg)
-  (raise (condition
-           (make-error)
-           (make-message-condition msg))))
-
-;;; Returns a boolean indicating success
-(define (read-exact! port offset len bv start)
-  (set-port-position! port offset)
-  (let ((nr (get-bytevector-n! port bv start len)))
-    (and (not (eof-object? nr))
-         (= len nr))))
-
-;;; Returns a 4k bytevector or #f
-(define (read-exact port offset len)
-  (let ((bv (make-bytevector len)))
-   (if (read-exact! port offset len bv 0) bv #f)))
-
-(define (read-block port b)
-  (or (read-exact port (* b metadata-block-size) metadata-block-size)
-      (io-error (fmt #f (dsp "Unable to read metadata block: ") (num b)))))
-
-;;; FIXME: implement a little block cache.
-
-
-;;;;---------------------------------------------------
-;;;; CRC32
-;;;;---------------------------------------------------
-
-;; FIXME: move to own library
-(load-shared-object "libz.so")
-(define crc32
-  (foreign-procedure "crc32" (unsigned-long u8* unsigned-int) unsigned-long))
-
-(define crc32-combine
-  (foreign-procedure "crc32_combine" (unsigned-long unsigned-long unsigned-long) unsigned-long))
-
-;; FIXME: stop copying the bytevector.  I'm not sure how to pass an offset into
-;; the bv.
-(define (crc32-region salt bv start end)
-  (assert (< start end))
-  (let ((len (- end start)))
-   (let ((copy (make-bytevector len)))
-    (bytevector-copy! bv start copy 0 len)
-    (let ((crc (crc32 salt copy 0)))
-     (crc32 crc copy len)))))
-
-;;;;---------------------------------------------------
-;;;; Decoding
-;;;;---------------------------------------------------
-
-(define-syntax unpack-type
-  (syntax-rules (le32 le64 bytes)
-    ((_ bv offset le32)
-     (bytevector-u32-ref bv offset (endianness little)))
-
-    ((_ bv offset le64)
-     (bytevector-u64-ref bv offset (endianness little)))
-
-    ((_ bv offset (bytes count))
-     (let ((copy (make-bytevector count)))
-      (bytevector-copy! bv offset copy 0 count)
-      copy))))
-
-(define (size-type t)
-  (syntax-case t (le32 le64 bytes)
-                 (le32 #'4)
-                 (le64 #'8)
-                 ((bytes count) #'count)))
-
-;;; FIXME: (bytes <count>) has to use a literal rather than a symbol.
-(define-syntax binary-format
-  (lambda (x)
-    (syntax-case x ()
-                 ((_ (name pack-name unpack-name) (field type) ...)
-                  (with-syntax ((((t o) ...)
-                                 (let f ((acc 0) (types #'(type ...)))
-                                  (if (null? types)
-                                      '()
-                                      (cons (list (car types) acc)
-                                            (f (+ (syntax->datum (size-type (car types))) acc) (cdr types)))))))
-                               #`(begin
-                                   (define-record-type name (fields field ...))
-
-                                   (define (unpack-name bv offset)
-                                     ((record-constructor (record-type-descriptor name))
-                                      (unpack-type bv (+ offset o) t) ...))))))))
-
 (binary-format (superblock pack-superblock unpack-superblock)
   (csum le32)
   (flags le32)
diff --git a/functional-tests/crc32.scm b/functional-tests/crc32.scm
new file mode 100644
index 0000000..c50d8d0
--- /dev/null
+++ b/functional-tests/crc32.scm
@@ -0,0 +1,23 @@
+(library
+  (crc32)
+  (export crc32)
+  (import (chezscheme))
+
+  (load-shared-object "libz.so")
+
+  (define crc32
+    (foreign-procedure "crc32" (unsigned-long u8* unsigned-int) unsigned-long))
+
+  (define crc32-combine
+    (foreign-procedure "crc32_combine" (unsigned-long unsigned-long unsigned-long) unsigned-long))
+
+  ;; FIXME: stop copying the bytevector.  I'm not sure how to pass an offset
+  ;; into the bv.
+  (define (crc32-region salt bv start end)
+    (assert (< start end))
+    (let ((len (- end start)))
+     (let ((copy (make-bytevector len)))
+      (bytevector-copy! bv start copy 0 len)
+      (let ((crc (crc32 salt copy 0)))
+       (crc32 crc copy len))))))
+