diff --git a/shell.js b/shell.js
index a3ef68c..4ba438d 100644
--- a/shell.js
+++ b/shell.js
@@ -364,6 +364,10 @@ exports.mv = wrap('mv', _mv);
 //@
 //@ + `p`: full path (will create intermediate dirs if necessary)
 //@
+//@ Examples:
+//@
+//@ + `mkdir('-p', '/tmp/a/b/c/d')`
+//@
 //@ Creates directories.
 function _mkdir(options, dirs) {
   options = parseOptions(options, {
@@ -398,6 +402,11 @@ exports.mkdir = wrap('mkdir', _mkdir);
 
 //@
 //@ #### cat(file [, file ...]')
+//@
+//@ Examples:
+//@
+//@ `var str = cat('file*.txt')`
+//@
 //@ Returns a string containing the given file, or a concatenated string
 //@ containing the files if more than one file is given (a new line character is
 //@ introduced between each file). Wildcard `*` accepted.
@@ -441,7 +450,7 @@ function _to(options, file) {
 String.prototype.to = wrap('to', _to);
 
 //@
-//@ #### sed(search_regex, 'replace_str', 'file' [, options])
+//@ #### sed([options ,] search_regex, 'replace_str', 'file')
 //@ Available options:
 //@
 //@ + `inplace`: (Default is `false`) If `true` will replace contents of 'file' with 
@@ -449,7 +458,11 @@ String.prototype.to = wrap('to', _to);
 //@
 //@ Reads an input string from `file` and performs a JavaScript `replace()` on the input
 //@ using the given search regex and replacement string. Returns the modified string.
-function _sed(options, regex, replacement, file, options) {
+function _sed(options, regex, replacement, file) {
+  options = parseOptions(options, {
+    'i': 'inplace'
+  });
+
   if (typeof replacement === 'string')
     replacement = replacement; // no-op
   else if (typeof replacement === 'number')
@@ -464,7 +477,7 @@ function _sed(options, regex, replacement, file, options) {
     error('no such file or directory: ' + file);
 
   var result = fs.readFileSync(file, 'utf8').replace(regex, replacement);
-  if (options && options.inplace)
+  if (options.inplace)
     result.to(file);
 
   return result;
@@ -772,7 +785,7 @@ function wrap(cmd, fn) {
 
     try {
       var args = [].slice.call(arguments, 0);
-      if (args.length === 0 || args[0][0] !== '-')
+      if (args.length === 0 || typeof args[0] !== 'string' || args[0][0] !== '-')
         args.unshift(''); // only add dummy option if '-option' not already present
       retValue = fn.apply(this, args);
     } catch (e) {
diff --git a/test/cat.js b/test/cat.js
index 7f88bb0..8842de6 100644
--- a/test/cat.js
+++ b/test/cat.js
@@ -16,6 +16,9 @@ function numLines(str) {
 // save current dir
 var cur = shell.pwd();
 
+shell.rm('-rf', 'tmp');
+shell.mkdir('tmp')
+
 //
 // Invalids
 //
diff --git a/test/cd.js b/test/cd.js
index f1e240c..ecb7cf0 100644
--- a/test/cd.js
+++ b/test/cd.js
@@ -16,6 +16,9 @@ function numLines(str) {
 // save current dir
 var cur = shell.pwd();
 
+shell.rm('-rf', 'tmp');
+shell.mkdir('tmp')
+
 //
 // Invalids
 //
diff --git a/test/cp.js b/test/cp.js
index 6228074..6628dee 100644
--- a/test/cp.js
+++ b/test/cp.js
@@ -13,6 +13,9 @@ function numLines(str) {
   return typeof str === 'string' ? str.match(/\n/g).length : 0;
 }
 
+shell.rm('-rf', 'tmp');
+shell.mkdir('tmp')
+
 //
 // Invalids
 //
diff --git a/test/env.js b/test/env.js
index 278272b..1859dee 100644
--- a/test/env.js
+++ b/test/env.js
@@ -4,6 +4,9 @@ var assert = require('assert');
 
 silent();
 
+shell.rm('-rf', 'tmp');
+shell.mkdir('tmp')
+
 //
 // Valids
 //
diff --git a/test/exists.js b/test/exists.js
index c7ead3d..2ac475a 100644
--- a/test/exists.js
+++ b/test/exists.js
@@ -16,6 +16,9 @@ function numLines(str) {
 // save current dir
 var cur = pwd();
 
+shell.rm('-rf', 'tmp');
+shell.mkdir('tmp')
+
 //
 // Invalids
 //
diff --git a/test/external.js b/test/external.js
index 74a55c3..1fc20a2 100644
--- a/test/external.js
+++ b/test/external.js
@@ -10,6 +10,9 @@ function numLines(str) {
   return typeof str === 'string' ? str.match(/\n/g).length : 0;
 }
 
+shell.rm('-rf', 'tmp');
+shell.mkdir('tmp')
+
 //
 // Invalids
 //
diff --git a/test/grep.js b/test/grep.js
index 1cb8851..76d3265 100644
--- a/test/grep.js
+++ b/test/grep.js
@@ -13,6 +13,9 @@ function numLines(str) {
   return typeof str === 'string' ? str.match(/\n/g).length : 0;
 }
 
+shell.rm('-rf', 'tmp');
+shell.mkdir('tmp')
+
 //
 // Invalids
 //
diff --git a/test/ls.js b/test/ls.js
index b1f1bcd..b490146 100644
--- a/test/ls.js
+++ b/test/ls.js
@@ -13,6 +13,9 @@ function numLines(str) {
   return typeof str === 'string' ? str.match(/\n/g).length : 0;
 }
 
+shell.rm('-rf', 'tmp');
+shell.mkdir('tmp')
+
 //
 // Invalids
 //
diff --git a/test/mkdir.js b/test/mkdir.js
index 8bf7f7d..338cff1 100644
--- a/test/mkdir.js
+++ b/test/mkdir.js
@@ -1,4 +1,4 @@
-require('../maker');
+var shell = require('..');
 
 var assert = require('assert'),
     path = require('path'),
@@ -7,27 +7,30 @@ var assert = require('assert'),
 // Node shims for < v0.7
 fs.existsSync = fs.existsSync || path.existsSync;
 
-silent();
+shell.silent();
 
 function numLines(str) {
   return typeof str === 'string' ? str.match(/\n/g).length : 0;
 }
 
+shell.rm('-rf', 'tmp');
+shell.mkdir('tmp')
+
 //
 // Invalids
 //
 
-mkdir();
-assert.ok(error());
+shell.mkdir();
+assert.ok(shell.error());
 
 var mtime = fs.statSync('tmp').mtime.toString();
-mkdir('tmp'); // dir already exists
-assert.ok(error());
+shell.mkdir('tmp'); // dir already exists
+assert.ok(shell.error());
 assert.equal(fs.statSync('tmp').mtime.toString(), mtime); // didn't mess with dir
 
 assert.equal(fs.existsSync('/asdfasdf'), false); // sanity check
-mkdir('/asdfasdf/asdfasdf'); // root path does not exist
-assert.ok(error());
+shell.mkdir('/asdfasdf/asdfasdf'); // root path does not exist
+assert.ok(shell.error());
 assert.equal(fs.existsSync('/asdfasdf'), false);
 
 //
@@ -35,35 +38,28 @@ assert.equal(fs.existsSync('/asdfasdf'), false);
 //
 
 assert.equal(fs.existsSync('tmp/t1'), false);
-mkdir('tmp/t1'); // simple dir
-assert.equal(error(), null);
+shell.mkdir('tmp/t1'); // simple dir
+assert.equal(shell.error(), null);
 assert.equal(fs.existsSync('tmp/t1'), true);
 
 assert.equal(fs.existsSync('tmp/t2'), false);
 assert.equal(fs.existsSync('tmp/t3'), false);
-mkdir('tmp/t2 tmp/t3'); // multiple dirs
-assert.equal(error(), null);
+shell.mkdir('tmp/t2', 'tmp/t3'); // multiple dirs
+assert.equal(shell.error(), null);
 assert.equal(fs.existsSync('tmp/t2'), true);
 assert.equal(fs.existsSync('tmp/t3'), true);
 
 assert.equal(fs.existsSync('tmp/t1'), true);
 assert.equal(fs.existsSync('tmp/t4'), false);
-mkdir('tmp/t1 tmp/t4'); // one dir exists, one doesn't
-assert.equal(numLines(error()), 1);
+shell.mkdir('tmp/t1', 'tmp/t4'); // one dir exists, one doesn't
+assert.equal(numLines(shell.error()), 1);
 assert.equal(fs.existsSync('tmp/t1'), true);
 assert.equal(fs.existsSync('tmp/t4'), true);
 
 assert.equal(fs.existsSync('tmp/a'), false);
-mkdir('-p tmp/a/b/c');
-assert.equal(error(), null);
+shell.mkdir('-p', 'tmp/a/b/c');
+assert.equal(shell.error(), null);
 assert.equal(fs.existsSync('tmp/a/b/c'), true);
-rm('-Rf tmp/a'); // revert
+shell.rm('-Rf', 'tmp/a'); // revert
 
-// comma-syntax
-assert.equal(fs.existsSync('tmp/a'), false);
-mkdir('-p', 'tmp/a/b/c tmp/d/e/f');
-assert.equal(error(), null);
-assert.equal(fs.existsSync('tmp/a/b/c'), true);
-assert.equal(fs.existsSync('tmp/d/e/f'), true);
-
-exit(123);
+shell.exit(123);
diff --git a/test/mv.js b/test/mv.js
index 3cb9051..cd8db00 100644
--- a/test/mv.js
+++ b/test/mv.js
@@ -13,11 +13,11 @@ function numLines(str) {
   return typeof str === 'string' ? str.match(/\n/g).length : 0;
 }
 
+shell.rm('-rf', 'tmp');
+shell.mkdir('tmp')
+
 // Prepare tmp/
-shell.rm('-rf', 'tmp/*');
-assert.equal(shell.error(), null);
 shell.cp('resources/*', 'tmp');
-assert.equal(shell.error(), null);
 
 //
 // Invalids
diff --git a/test/pwd.js b/test/pwd.js
index 34b2f6e..26c704a 100644
--- a/test/pwd.js
+++ b/test/pwd.js
@@ -9,6 +9,9 @@ function numLines(str) {
   return typeof str === 'string' ? str.match(/\n/g).length : 0;
 }
 
+shell.rm('-rf', 'tmp');
+shell.mkdir('tmp')
+
 //
 // Valids
 //
diff --git a/test/rm.js b/test/rm.js
index cbde770..a023ac7 100644
--- a/test/rm.js
+++ b/test/rm.js
@@ -9,6 +9,9 @@ fs.existsSync = fs.existsSync || path.existsSync;
 
 silent();
 
+shell.rm('-rf', 'tmp');
+shell.mkdir('tmp')
+
 //
 // Invalids
 //
diff --git a/test/sed.js b/test/sed.js
index e433ac2..4b78ea8 100644
--- a/test/sed.js
+++ b/test/sed.js
@@ -1,4 +1,4 @@
-require('../maker');
+var shell = require('..');
 
 var assert = require('assert'),
     path = require('path'),
@@ -7,49 +7,52 @@ var assert = require('assert'),
 // Node shims for < v0.7
 fs.existsSync = fs.existsSync || path.existsSync;
 
-silent();
+shell.silent();
 
 function numLines(str) {
   return typeof str === 'string' ? str.match(/\n/g).length : 0;
 }
 
+shell.rm('-rf', 'tmp');
+shell.mkdir('tmp')
+
 //
 // Invalids
 //
 
-sed();
-assert.ok(error());
+shell.sed();
+assert.ok(shell.error());
 
-sed(/asdf/g); // too few args
-assert.ok(error());
+shell.sed(/asdf/g); // too few args
+assert.ok(shell.error());
 
-sed(/asdf/g, 'nada'); // too few args
-assert.ok(error());
+shell.sed(/asdf/g, 'nada'); // too few args
+assert.ok(shell.error());
 
 assert.equal(fs.existsSync('/asdfasdf'), false); // sanity check
-sed(/asdf/g, 'nada', '/asdfasdf'); // no such file
-assert.ok(error());
+shell.sed(/asdf/g, 'nada', '/asdfasdf'); // no such file
+assert.ok(shell.error());
 
 //
 // Valids
 //
 
-cp('-f resources/file1 tmp/file1')
-var result = sed('test1', 'hello', 'tmp/file1'); // search string
-assert.equal(error(), null);
+shell.cp('-f', 'resources/file1', 'tmp/file1')
+var result = shell.sed('test1', 'hello', 'tmp/file1'); // search string
+assert.equal(shell.error(), null);
 assert.equal(result, 'hello');
 
-var result = sed(/test1/, 'hello', 'tmp/file1'); // search regex
-assert.equal(error(), null);
+var result = shell.sed(/test1/, 'hello', 'tmp/file1'); // search regex
+assert.equal(shell.error(), null);
 assert.equal(result, 'hello');
 
-var result = sed(/test1/, 1234, 'tmp/file1'); // numeric replacement
-assert.equal(error(), null);
+var result = shell.sed(/test1/, 1234, 'tmp/file1'); // numeric replacement
+assert.equal(shell.error(), null);
 assert.equal(result, '1234');
 
-var result = sed(/test1/, 'hello', 'tmp/file1', {inplace:true});
-assert.equal(error(), null);
+var result = shell.sed('-i', /test1/, 'hello', 'tmp/file1');
+assert.equal(shell.error(), null);
 assert.equal(result, 'hello');
-assert.equal(cat('tmp/file1'), 'hello');
+assert.equal(shell.cat('tmp/file1'), 'hello');
 
-exit(123);
+shell.exit(123);
diff --git a/test/tempdir.js b/test/tempdir.js
index 65ea822..d8c3d7e 100644
--- a/test/tempdir.js
+++ b/test/tempdir.js
@@ -13,6 +13,9 @@ function numLines(str) {
   return typeof str === 'string' ? str.match(/\n/g).length : 0;
 }
 
+shell.rm('-rf', 'tmp');
+shell.mkdir('tmp')
+
 //
 // Valids
 //
diff --git a/test/to.js b/test/to.js
index def09a4..5257b6c 100644
--- a/test/to.js
+++ b/test/to.js
@@ -13,6 +13,9 @@ function numLines(str) {
   return typeof str === 'string' ? str.match(/\n/g).length : 0;
 }
 
+shell.rm('-rf', 'tmp');
+shell.mkdir('tmp')
+
 //
 // Invalids
 //