diff --git a/Gemfile.lock b/Gemfile.lock
index 3509d0a..7449551 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -6,7 +6,12 @@ PATH
 GEM
   remote: https://rubygems.org/
   specs:
+    coderay (1.1.3)
+    method_source (1.0.0)
     minitest (5.16.3)
+    pry (0.14.1)
+      coderay (~> 1.1)
+      method_source (~> 1.0)
     rake (13.0.6)
 
 PLATFORMS
@@ -16,6 +21,7 @@ DEPENDENCIES
   bundler (~> 2.3)
   minitest (~> 5.16)
   minitest-thesis!
+  pry (~> 0.14)
   rake (~> 13.0)
 
 BUNDLED WITH
diff --git a/lib/minitest/thesis.rb b/lib/minitest/thesis.rb
index 08583db..5c59633 100644
--- a/lib/minitest/thesis.rb
+++ b/lib/minitest/thesis.rb
@@ -104,7 +104,7 @@ module Minitest
       def just(value) = Possibility.new("just(#{value})") { value }
 
       # No possible values. i.e. Any call to `any` will reject the test case.
-      def nothing = Possibility.new {|tc| tc.reject }
+      def nothing = Possibility.new("nothing") {|tc| tc.reject }
 
       # Possible values can be any value possible for one of `possibilities`.
       def mix_of(*possibilities)
diff --git a/lib/minitest/thesis/possibility.rb b/lib/minitest/thesis/possibility.rb
index 8f24e81..37b54bc 100644
--- a/lib/minitest/thesis/possibility.rb
+++ b/lib/minitest/thesis/possibility.rb
@@ -5,7 +5,7 @@ module Minitest::Thesis
   class Possibility
     attr_reader :produce, :name
 
-    def initialize(name = "TODO", &produce)
+    def initialize(name, &produce)
       @name = name
       @produce = produce
     end
@@ -15,20 +15,20 @@ module Minitest::Thesis
 
     # "Returns a `Possibility` where values come from applying `f` to some possible value for `self`."
     def map(&f)
-      self.class.new("#{name}.map(TODO)") {|tc| f.call(tc.any(self)) }
+      self.class.new("#{name}.map(#{f.class})") {|tc| f.call(tc.any(self)) }
     end
 
     # Returns a `Possibility` where values come from applying `f` (which
     # should return a new `Possibility` to some possible value for `self`
     # then returning a possible value from that.
     def bind(&f)
-      self.class.new("#{name}.bind(TODO)") {|tc| tc.any(f.(tc.any(self))) }
+      self.class.new("#{name}.bind(#{f.class})") {|tc| tc.any(f.(tc.any(self))) }
     end
 
     # Returns a `Possibility` whose values are any possible value of `self`
     # for which `f` returns True.
     def satisfying(&f)
-      self.class.new("#{name}.select(TODO)") {|test_case|
+      self.class.new("#{name}.select(#{f.class})") {|test_case|
         3.times.first {
           candidate = test_case.any(self)
           candidate if f.(candidate)
diff --git a/minitest-thesis.gemspec b/minitest-thesis.gemspec
index da221cc..b2fd088 100644
--- a/minitest-thesis.gemspec
+++ b/minitest-thesis.gemspec
@@ -38,4 +38,5 @@ Gem::Specification.new do |spec|
   spec.add_development_dependency "bundler", "~> 2.3"
   spec.add_development_dependency "rake", "~> 13.0"
   spec.add_development_dependency "minitest", "~> 5.16"
+  spec.add_development_dependency "pry", "~> 0.14"
 end