diff --git a/cranelift/src/tools/filetest/mod.rs b/cranelift/src/tools/filetest/mod.rs
index b368959125..9126efbfc0 100644
--- a/cranelift/src/tools/filetest/mod.rs
+++ b/cranelift/src/tools/filetest/mod.rs
@@ -4,7 +4,10 @@
 //! available test commands.
 
 use std::path::Path;
+use cton_reader::TestCommand;
 use CommandResult;
+use cat;
+use print_cfg;
 use filetest::runner::TestRunner;
 
 pub mod subtest;
@@ -34,3 +37,17 @@ pub fn run(files: Vec<String>) -> CommandResult {
 
     runner.run()
 }
+
+/// Create a new subcommand trait object to match `parsed.command`.
+///
+/// This function knows how to create all of the possible `test <foo>` commands that can appear in
+/// a .cton test file.
+fn new_subtest(parsed: &TestCommand) -> subtest::Result<Box<subtest::SubTest>> {
+    match parsed.command {
+        "cat" => cat::subtest(parsed),
+        "print-cfg" => print_cfg::subtest(parsed),
+        "domtree" => domtree::subtest(parsed),
+        "verifier" => verifier::subtest(parsed),
+        _ => Err(format!("unknown test command '{}'", parsed.command)),
+    }
+}
diff --git a/cranelift/src/tools/filetest/runner.rs b/cranelift/src/tools/filetest/runner.rs
index 5f9fac9713..8c9ea87810 100644
--- a/cranelift/src/tools/filetest/runner.rs
+++ b/cranelift/src/tools/filetest/runner.rs
@@ -15,6 +15,7 @@ use utils::read_to_string;
 use cton_reader::parse_test;
 use cretonne::ir::Function;
 use cretonne::verify_function;
+use filetest::new_subtest;
 use filetest::subtest::{self, SubTest, Context};
 
 type TestResult = Result<time::Duration, String>;
@@ -218,7 +219,7 @@ impl Job {
         }
         // Parse the test commands.
         let mut tests =
-            try!(testfile.commands.iter().map(subtest::new).collect::<subtest::Result<Vec<_>>>());
+            try!(testfile.commands.iter().map(new_subtest).collect::<subtest::Result<Vec<_>>>());
 
         // Sort the tests so the mutators are at the end, and those that
         // don't need the verifier are at the front
diff --git a/cranelift/src/tools/filetest/subtest.rs b/cranelift/src/tools/filetest/subtest.rs
index cfc5cec5bf..b958193cd8 100644
--- a/cranelift/src/tools/filetest/subtest.rs
+++ b/cranelift/src/tools/filetest/subtest.rs
@@ -3,26 +3,11 @@
 use std::result;
 use std::borrow::Cow;
 use cretonne::ir::Function;
-use cton_reader::{TestCommand, Details};
+use cton_reader::Details;
 use filecheck::{self, CheckerBuilder, Checker, Value as FCValue};
 
 pub type Result<T> = result::Result<T, String>;
 
-/// Create a new subcommand trait object to match `parsed.command`.
-pub fn new(parsed: &TestCommand) -> Result<Box<SubTest>> {
-    use cat;
-    use print_cfg;
-    use filetest::domtree;
-    use filetest::verifier;
-    match parsed.command {
-        "cat" => cat::subtest(parsed),
-        "print-cfg" => print_cfg::subtest(parsed),
-        "domtree" => domtree::subtest(parsed),
-        "verifier" => verifier::subtest(parsed),
-        _ => Err(format!("unknown test command '{}'", parsed.command)),
-    }
-}
-
 /// Context for running a a test on a single function.
 pub struct Context<'a> {
     /// Additional details about the function from the parser.