diff --git a/tested/cat/.gitignore b/tested/cat/.gitignore
new file mode 100644
index 0000000..a7053b1
--- /dev/null
+++ b/tested/cat/.gitignore
@@ -0,0 +1,2 @@
+cat
+cat.exe
diff --git a/tested/cat/cat_test.go b/tested/cat/cat_test.go
new file mode 100644
index 0000000..f3db0dd
--- /dev/null
+++ b/tested/cat/cat_test.go
@@ -0,0 +1,32 @@
+package main
+
+import (
+  "testing"
+  "github.com/stretchr/testify/assert"
+  "os"
+)
+
+func WithArgs(args []string, test func ()) {
+  old_args := os.Args
+  defer (func() { os.Args = old_args })()
+  os.Args = args
+  test()
+}
+
+func TestParseOpts(t *testing.T) {
+  args := []string{"cat.exe", "-n", "main.go"}
+
+  WithArgs(args, func () {
+    opts := ParseOpts()
+    assert.Equal(t, opts.Number, true, "-n didn't work")
+  })
+
+  /*
+  // This fails because flag can't be run more than once
+  args = []string{"cat.exe", "-s", "main.go"}
+  WithArgs(args, func () {
+    opts := ParseOpts()
+    assert.Equal(t, opts.Squeeze, true, "-s didn't work")
+  })
+  */
+}
diff --git a/tested/cat/go.mod b/tested/cat/go.mod
new file mode 100644
index 0000000..6c3a0f7
--- /dev/null
+++ b/tested/cat/go.mod
@@ -0,0 +1,11 @@
+module lcthw.dev/go/go-coreutils/cat
+
+go 1.24.2
+
+require github.com/stretchr/testify v1.11.1
+
+require (
+	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
+)
diff --git a/tested/cat/go.sum b/tested/cat/go.sum
new file mode 100644
index 0000000..c4c1710
--- /dev/null
+++ b/tested/cat/go.sum
@@ -0,0 +1,10 @@
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/testify v1.11.1 h1:7s2iGBzp5EwR7/aIZr8ao5+dra3wiQyKjjFuvgVKu7U=
+github.com/stretchr/testify v1.11.1/go.mod h1:wZwfW3scLgRK+23gO65QZefKpKQRnfz6sD981Nm4B6U=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
diff --git a/tested/cat/main.go b/tested/cat/main.go
new file mode 100644
index 0000000..fc6686b
--- /dev/null
+++ b/tested/cat/main.go
@@ -0,0 +1,58 @@
+package main
+
+import (
+  "fmt"
+  "flag"
+  "os"
+  "log"
+  "strings"
+)
+
+type Opts struct {
+  Number bool
+  Squeeze bool
+  Filenames []string
+}
+
+func ParseOpts() (Opts) {
+  var opts Opts
+
+  fmt.Println("args:", os.Args)
+
+  flag.BoolVar(&opts.Number, "n", false, "Number all nonempty output lines, starting with 1")
+  flag.BoolVar(&opts.Squeeze, "s", false, "Suppress repeated adjacent blank lines")
+  flag.Parse()
+
+  if flag.NArg() < 1 {
+    log.Fatal("USAGE: cat [-n] [-s] file0 [fileN]")
+    os.Exit(1)
+  }
+
+  opts.Filenames = flag.Args()
+
+  return opts
+}
+
+func main() {
+  opts := ParseOpts()
+
+  for _, filename := range opts.Filenames {
+    in_file, err := os.ReadFile(filename)
+
+    if err != nil { log.Fatalf("cannot open %s: %v", filename, err) }
+
+    if(opts.Number) {
+      count := 1
+      for line := range strings.Lines(string(in_file)) {
+        if opts.Squeeze && len(line) <= 1 {
+          continue
+        }
+
+        fmt.Printf("%0.4d: %s", count, line)
+        count++
+      }
+    } else {
+      fmt.Print(string(in_file))
+    }
+  }
+}
diff --git a/tested/od/.gitignore b/tested/od/.gitignore
new file mode 100644
index 0000000..f2e57ad
--- /dev/null
+++ b/tested/od/.gitignore
@@ -0,0 +1,2 @@
+od
+od.exe
diff --git a/tested/od/go.mod b/tested/od/go.mod
new file mode 100644
index 0000000..625e69c
--- /dev/null
+++ b/tested/od/go.mod
@@ -0,0 +1,11 @@
+module lcthw.dev/go/go-coreutils/od
+
+go 1.24.2
+
+require github.com/stretchr/testify v1.11.1
+
+require (
+	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
+)
diff --git a/tested/od/go.sum b/tested/od/go.sum
new file mode 100644
index 0000000..c4c1710
--- /dev/null
+++ b/tested/od/go.sum
@@ -0,0 +1,10 @@
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/testify v1.11.1 h1:7s2iGBzp5EwR7/aIZr8ao5+dra3wiQyKjjFuvgVKu7U=
+github.com/stretchr/testify v1.11.1/go.mod h1:wZwfW3scLgRK+23gO65QZefKpKQRnfz6sD981Nm4B6U=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
diff --git a/tested/od/main.go b/tested/od/main.go
new file mode 100644
index 0000000..9409942
--- /dev/null
+++ b/tested/od/main.go
@@ -0,0 +1,67 @@
+package main
+
+import (
+  "fmt"
+  "os"
+  "flag"
+  "log"
+  "bufio"
+)
+
+type Opts struct {
+  Width int
+  Filenames []string
+  Hex bool
+  Octal bool
+  Format string
+}
+
+func ParseOpts(args []string) (Opts) {
+  var opts Opts
+  myflags := flag.NewFlagSet("od", flag.ContinueOnError)
+
+  myflags.IntVar(&opts.Width, "w", 16, "Width of output grid")
+  myflags.BoolVar(&opts.Hex, "x", false, "Output hex bytes")
+  myflags.BoolVar(&opts.Octal, "o", false, "Output octal bytes")
+
+  myflags.Parse(args[1:])
+
+  if myflags.NArg() == 0 {
+    log.Fatal("USAGE: od [files]")
+  }
+
+  if opts.Hex {
+    opts.Format = "%0.2x "
+  } else {
+    opts.Format = "%0.3o "
+  }
+
+  opts.Filenames = myflags.Args()
+  return opts
+}
+
+func main() {
+  opts := ParseOpts(os.Args)
+
+  for _, filename := range opts.Filenames {
+    reader, err := os.Open(filename)
+    defer reader.Close()
+    if err != nil { log.Fatalf("can't open: %s: %v", filename, err) }
+
+    buf := bufio.NewReader(reader)
+    count := buf.Size()
+
+    fmt.Printf("%0.8o ", 0);
+
+    for index := 0; index < count; index++ {
+      data, err := buf.ReadByte()
+      if err != nil { break }
+      fmt.Printf(opts.Format, data);
+
+      if (index + 1) % opts.Width == 0 {
+        fmt.Print("\n")
+        fmt.Printf("%0.8o ", index);
+      }
+    }
+  }
+}
diff --git a/tested/od/od_test.go b/tested/od/od_test.go
new file mode 100644
index 0000000..db0aa10
--- /dev/null
+++ b/tested/od/od_test.go
@@ -0,0 +1,17 @@
+package main
+
+import (
+  "testing"
+  "github.com/stretchr/testify/assert"
+)
+
+func TestParseOpts(t *testing.T) {
+  args := []string{"od.exe", "-x", "main.go"}
+  opts := ParseOpts(args)
+  assert.Equal(t, opts.Hex, true, "-x didn't work")
+
+  // This fails because flag can't be run more than once
+  args = []string{"cat.exe", "-o", "main.go"}
+  opts = ParseOpts(args)
+  assert.Equal(t, opts.Octal, true, "-o didn't work")
+}