diff --git a/Rakefile.rb b/Rakefile.rb
index 1a83eee..2e95728 100644
--- a/Rakefile.rb
+++ b/Rakefile.rb
@@ -19,7 +19,6 @@ end
 RSpec::Core::RakeTask.new(:spec, :example_string) do |task, args|
   ENV["specs"] = "1"
   if args.example_string
-    ENV["partial_specs"] = "1"
     task.rspec_opts = %W[-e "#{args.example_string}" -f documentation]
   end
 end
@@ -27,6 +26,13 @@ task :spec => :build_dist
 task :spec do
   ENV.delete("specs")
 end
+task :spec => :build_tests
+
+task :build_tests do |task, args|
+  ENV["specs"] = "1"
+  sh "ruby -Ilib build_tests/build_tests.rb"
+  ENV.delete("specs")
+end
 
 # dspec task is useful to test the distributable release script, but is not
 # useful for coverage information.
diff --git a/build_tests/build_tests.rb b/build_tests/build_tests.rb
index a738508..89e9895 100644
--- a/build_tests/build_tests.rb
+++ b/build_tests/build_tests.rb
@@ -1,10 +1,15 @@
+#!/usr/bin/env ruby
+
+require "bundler"
 require "fileutils"
 require "open3"
 require "set"
 require "tmpdir"
+require "rscons"
 
 BASE_DIR = File.expand_path("build_test_run")
 OWD = Dir.pwd
+TESTS_LINE = File.read(__FILE__).lines.find_index {|line| line.chomp == "# Tests"}
 
 RunResults = Struct.new(:stdout, :stderr, :status)
 
@@ -25,14 +30,18 @@ class Test
   def run(outfh)
     failure = false
     begin
-      self.instance_eval(@block)
+      self.instance_eval(&@block)
       @output += "<pass>" if @output == ""
     rescue RuntimeError => re
-      @output += re.message
+      @output += re.message + "\n"
       # TODO:
-#      if test.exception.backtrace.find {|e| e =~ %r{^(.*/#{File.basename(__FILE__)}:\d+)}}
-#        message += " (#{$1})"
-#      end
+      re.backtrace.each do |line|
+        if line =~ %r{^(.*/#{File.basename(__FILE__)}:(\d+))}
+          if $2.to_i > TESTS_LINE
+            @output += "#{$1}\n"
+          end
+        end
+      end
       @output += "Keeping directory #{@run_dir} for inspection"
       failure = true
     end
@@ -94,6 +103,7 @@ end
 SimpleCov.start do
   root(#{OWD.inspect})
   coverage_dir(#{@coverage_dir.inspect})
+  command_name "build_tests"
   filters.clear
   add_filter do |src|
     !(src.filename[SimpleCov.root])
@@ -173,13 +183,13 @@ EOF
   end
 
   def expect_match(a, b)
-    unless a ~= b
+    unless a =~ b
       raise "Expected #{a.inspect} to match #{b.inspect}"
     end
   end
 
   def expect_not_match(a, b)
-    if a ~= b
+    if a =~ b
       raise "Expected #{a.inspect} to not match #{b.inspect}"
     end
   end
@@ -230,6 +240,7 @@ def rm_rf(dir)
 end
 
 def run_tests
+  $stdout.sync = true
   rm_rf(BASE_DIR)
   FileUtils.mkdir_p(BASE_DIR)
   keep_run_dir = false
@@ -268,6 +279,7 @@ def run_tests
       threads[thread] = [piper, pipew, test]
     end
   end
+  $stdout.write("\n")
   unless failure
     rm_rf(BASE_DIR)
   end
@@ -416,7 +428,7 @@ test "supports barriers and prevents parallelizing builders across them" do
   result = run_rscons(args: %w[-f barrier.rb -j 3])
   expect_eq(result.stderr, "")
   slines = lines(result.stdout).select {|line| line =~ /T\d/}
-  expect_eq(slines, [)
+  expect_eq(slines, [
     "[1/6] ThreadedTestBuilder T3",
     "[2/6] ThreadedTestBuilder T2",
     "[3/6] ThreadedTestBuilder T1",
@@ -429,7 +441,7 @@ test "supports barriers and prevents parallelizing builders across them" do
     "T4 finished",
     "T5 finished",
     "T6 finished",
-  ]
+  ])
 end
 
 test "expands target and source paths starting with ^/ and ^^/" do
@@ -753,7 +765,7 @@ test "rebuilds when user-specified dependencies using ^ change" do
   expect_eq(result.stderr, "")
   verify_lines(lines(result.stdout), [%r{Linking .*simple.exe}])
 
-  result = run_rscons(args: %w[-f user_dependencies_carat.rb])
+  result = run_rscons(args: %w[-f user_dependencies_carat.rb], env: {"file_contents" => "2"})
   expect_eq(result.stderr, "")
   expect_eq(result.stdout, "")
 end
@@ -1810,7 +1822,7 @@ context "SharedLibrary builder" do
     test_dir "shared_library"
     result = run_rscons(args: %w[-f shared_library_from_object.rb])
     expect_eq(result.stderr, "")
-    expect(File.exist?("one.c.o"))
+    expect(File.exist?("one.o"))
   end
 end
 
@@ -1954,7 +1966,7 @@ context "configure task" do
     result = run_rscons(args: %w[-f configure_with_top_level_env.rb configure --prefix=/yodabob])
     expect_eq(result.stderr, "")
     expect_eq(result.status, 0)
-    expect_match(result.stdout, "Prefix is /yodabob")
+    expect_match(result.stdout, %r{Prefix is /yodabob})
   end
 
   test "does not configure for distclean operation" do
@@ -3018,7 +3030,7 @@ EOF
     expect_eq(result.stderr, "")
     result = run_rscons(args: %w[-f Rsconscript_samedir])
     expect_eq(result.stderr, "")
-    expect_not_match(result.stdout, %{(Entering|Leaving) directory})
+    expect_not_match(result.stdout, %r{(Entering|Leaving) directory})
     verify_lines(lines(result.stdout), [
       %r{second build},
       %r{top build},
@@ -3522,3 +3534,5 @@ test "supports building LLVM assembly files with the Program builder in direct m
   expect_truthy(File.exist?("llvmtest.exe"))
   expect_match(`./llvmtest.exe`, /hello again/)
 end
+
+run_tests