diff --git a/features/thin_delta.feature b/features/thin_delta.feature
deleted file mode 100644
index 4363a9e..0000000
--- a/features/thin_delta.feature
+++ /dev/null
@@ -1,62 +0,0 @@
-Feature: thin_delta
-  Scenario: print version (-V flag)
-    When I run `thin_delta -V`
-    Then it should pass with version
-
-  Scenario: print version (--version flag)
-    When I run `thin_delta --version`
-    Then it should pass with version
-
-  Scenario: print help
-    When I run `thin_delta --help`
-    Then it should pass with:
-
-    """
-    Usage: thin_delta [options] <device or file>
-    Options:
-      {--thin1, --snap1}
-      {--thin2, --snap2}
-      {-m, --metadata-snap} [block#]
-      {--verbose}
-      {-h|--help}
-      {-V|--version}
-    """
-
-  Scenario: print help
-    When I run `thin_delta -h`
-    Then it should pass with:
-    """
-    Usage: thin_delta [options] <device or file>
-    Options:
-      {--thin1, --snap1}
-      {--thin2, --snap2}
-      {-m, --metadata-snap} [block#]
-      {--verbose}
-      {-h|--help}
-      {-V|--version}
-    """
-
-  Scenario: Unrecognised option should cause failure
-    When I run `thin_delta --unleash-the-hedeghogs`
-    Then it should fail
-
-  Scenario: --snap1 must be specified
-    When I run `thin_delta --snap2 45 foo`
-    Then it should fail with:
-    """
-    --snap1 not specified.
-    """
-
-  Scenario: --snap2 must be specified
-    When I run `thin_delta --snap1 45 foo`
-    Then it should fail with:
-    """
-    --snap2 not specified.
-    """
-
-  Scenario: device must be specified
-    When I run `thin_delta --snap1 45 --snap2 50`
-    Then it should fail with:
-    """
-    No input device provided.
-    """
diff --git a/functional-tests/scenario-string-constants.scm b/functional-tests/scenario-string-constants.scm
index f605e44..8c870d4 100644
--- a/functional-tests/scenario-string-constants.scm
+++ b/functional-tests/scenario-string-constants.scm
@@ -5,6 +5,7 @@
           thin-restore-outfile-too-small-text
           thin-restore-help
           thin-rmap-help
+          thin-delta-help
 
           cache-check-help
           cache-restore-help
@@ -54,6 +55,16 @@ Where:
   <block range> is of the form <begin>..<one-past-the-end>
   for example 5..45 denotes blocks 5 to 44 inclusive, but not block 45")
 
+  (define thin-delta-help
+    "Usage: thin_delta [options] <device or file>
+Options:
+  {--thin1, --snap1}
+  {--thin2, --snap2}
+  {-m, --metadata-snap} [block#]
+  {--verbose}
+  {-h|--help}
+  {-V|--version}")
+
   (define cache-check-help
     "Usage: cache_check [options] {device|file}
 Options:
@@ -105,4 +116,5 @@ Options:
 
 These all relate to the size of the fast device (eg, SSD), rather
 than the whole cached device.")
+
 )
diff --git a/functional-tests/thin-functional-tests.scm b/functional-tests/thin-functional-tests.scm
index 8767391..46e43ff 100644
--- a/functional-tests/thin-functional-tests.scm
+++ b/functional-tests/thin-functional-tests.scm
@@ -227,5 +227,48 @@
    (define-scenario (thin-rmap multiple-regions-should-pass)
                     "thin_rmap should handle multiple regions."
                     (with-valid-metadata (md)
-                      (thin-rmap "--region 1..23 --region 45..78" md))))
+                      (thin-rmap "--region 1..23 --region 45..78" md)))
 
+   ;;;-----------------------------------------------------------
+   ;;; thin_delta scenarios
+   ;;;-----------------------------------------------------------
+   (define-scenario (thin-delta v)
+                    "thin_delta accepts -V"
+                    (receive (stdout _) (thin-delta "-V")
+                             (assert-equal tools-version stdout)))
+
+   (define-scenario (thin-delta version)
+                    "thin_delta accepts --version"
+                    (receive (stdout _) (thin-delta "--version")
+                             (assert-equal tools-version stdout)))
+
+   (define-scenario (thin-delta h)
+                    "thin_delta accepts -h"
+                    (receive (stdout _) (thin-delta "-h")
+                             (assert-equal thin-delta-help stdout)))
+
+   (define-scenario (thin-delta help)
+                    "thin_delta accepts --help"
+                    (receive (stdout _) (thin-delta "--help")
+                             (assert-equal thin-delta-help stdout)))
+
+   (define-scenario (thin-delta unrecognised-option)
+                    "Unrecognised option should cause failure"
+                    (run-fail "thin_delta --unleash-the-hedgehogs"))
+
+   (define-scenario (thin-delta snap1-unspecified)
+                    "Fails without --snap1 fails"
+                    (receive (_ stderr) (run-fail "thin_delta --snap2 45 foo")
+                             (assert-starts-with "--snap1 not specified." stderr)))
+
+   (define-scenario (thin-delta snap2-unspecified)
+                    "Fails without --snap2 fails"
+                    (receive (_ stderr) (run-fail "thin_delta --snap1 45 foo")
+                             (assert-starts-with "--snap2 not specified." stderr)))
+
+   (define-scenario (thin-delta device-unspecified)
+                    "Fails if no device given"
+                    (receive (_ stderr) (run-fail "thin_delta --snap1 45 --snap2 46")
+                             (assert-starts-with "No input device provided." stderr)))
+
+)