diff --git a/common_test.go b/common_test.go
new file mode 100644
index 0000000..30c6a75
--- /dev/null
+++ b/common_test.go
@@ -0,0 +1,13 @@
+package jsh
+
+import "testing"
+
+func TestToJson(t *testing.T) {
+	fixture := JshOutput{[]string{}, []string{}}
+	json := fixture.ToJson()
+	expected := "{\"StdOut\":[],\"StdErr\":[]}"
+	actual := *json
+	if actual != expected {
+		t.Error("Empty fixture did not match:\n%s != %s", expected, actual)
+	}
+}
diff --git a/process_test.go b/process_test.go
new file mode 100644
index 0000000..d7ddeb9
--- /dev/null
+++ b/process_test.go
@@ -0,0 +1,28 @@
+package jsh
+
+import "testing"
+
+func TestNewProcess(t *testing.T) {
+	tooManyArgs := []string{"1", "2", "3", "4", "5", "6", "7", "8", "9", "10", "11", "12"}
+	_, err := NewProcess(tooManyArgs)
+	if err == nil {
+		t.Errorf("Passing 12 strings should raise an error")
+	}
+
+	tooFewArgs := []string{"1", "2", "3", "4", "5", "6", "7", "8", "9", "10"}
+	_, err = NewProcess(tooFewArgs)
+	if err == nil {
+		t.Errorf("Passing 10 strings should raise an error")
+	}
+
+	justRightArgs := []string{"1", "2", "3", "4", "5", "6", "7", "8", "9", "10", "11"}
+	proc, err := NewProcess(justRightArgs)
+	if err != nil {
+		t.Errorf("Passing 11 strings should not raise an error")
+	}
+	expected := Process{"1", "2", "3", "4", "5", "6", "7", "8", "9", "10", "11"}
+	actual := *proc
+	if expected != actual {
+		t.Errorf("Proc was incorrectly generated:\n%s != %s", expected, actual)
+	}
+}
diff --git a/ps/main.go b/ps/main.go
index 9edfc2a..730a844 100644
--- a/ps/main.go
+++ b/ps/main.go
@@ -4,49 +4,25 @@ import (
 	"flag"
 	"fmt"
 	"jsh"
-	"math"
 	"os"
 	"os/exec"
 	"strings"
-	"unicode"
 )
 
-// FieldsN slices s into substrings after each instance of a whitespace
-// character (according to unicode.IsSpace) and returns a slice of those
-// substrings. The slice's length is guaranteed to be at most maxN, and
-// all leftover fields are put into the last substring.
-func FieldsN(s string, maxN int) []string {
-	// First count the fields.
-	n := 0
-	inField := false
-	for _, rune := range s {
-		wasInField := inField
-		inField = !unicode.IsSpace(rune)
-		if inField && !wasInField {
-			n++
-		}
-	}
-	n = int(math.Min(float64(n), float64(maxN)))
+// Converts raw output of "ps" into a slice of Process objects
+func PsOutputToProcesses(out string) *[]jsh.Process {
+	processes := []jsh.Process{}
+	lines := strings.Split(out, "\n")
+	header, procs := lines[0], lines[1:]
+	numFields := len(strings.Fields(header))
 
-	// Now create them.
-	a := make([]string, n)
-	na := 0
-	fieldStart := -1 // Set to -1 when looking for start of field.
-	for i, rune := range s {
-		if unicode.IsSpace(rune) && na+1 < maxN {
-			if fieldStart >= 0 {
-				a[na] = s[fieldStart:i]
-				na++
-				fieldStart = -1
-			}
-		} else if fieldStart == -1 {
-			fieldStart = i
+	for _, proc := range procs {
+		p, err := jsh.NewProcess(jsh.FieldsN(proc, numFields))
+		if err == nil {
+			processes = append(processes, *p)
 		}
 	}
-	if fieldStart >= 0 { // Last field might end at EOF.
-		a[na] = s[fieldStart:]
-	}
-	return a
+	return &processes
 }
 
 // Falls back to procps-ng passing the space-separated arguments in the given
@@ -68,27 +44,11 @@ func fallbackCompletely() *[]byte {
 	return fallbackCompletelyWithArgs(nil)
 }
 
-// Converts raw output of "ps" into a slice of Process objects
-func psOutputToProcesses(out string) *[]jsh.Process {
-	processes := []jsh.Process{}
-	lines := strings.Split(out, "\n")
-	header, procs := lines[0], lines[1:]
-	numFields := len(strings.Fields(header))
-
-	for _, proc := range procs {
-		p, err := jsh.NewProcess(FieldsN(proc, numFields))
-		if err == nil {
-			processes = append(processes, *p)
-		}
-	}
-	return &processes
-}
-
 func runJsonMode() {
 	// Run procps-ng "ps" with full output
 	psOut := string(*fallbackCompletelyWithArgs([]string{"auxww"}))
 
-	processesPtr := psOutputToProcesses(psOut)
+	processesPtr := PsOutputToProcesses(psOut)
 	finalOut := jsh.JshOutput{*processesPtr, []string{}}
 	fmt.Printf("%s", *finalOut.ToJson())
 }
diff --git a/ps/main_test.go b/ps/main_test.go
new file mode 100644
index 0000000..a2b92b7
--- /dev/null
+++ b/ps/main_test.go
@@ -0,0 +1,7 @@
+package main
+
+import "testing"
+
+func TestPsOutputToProcesses(t *testing.T) {
+
+}
diff --git a/utils.go b/utils.go
new file mode 100644
index 0000000..19cc85e
--- /dev/null
+++ b/utils.go
@@ -0,0 +1,44 @@
+package jsh
+
+import (
+	"math"
+	"unicode"
+)
+
+// FieldsN slices s into substrings after each instance of a whitespace
+// character (according to unicode.IsSpace) and returns a slice of those
+// substrings. The slice's length is guaranteed to be at most maxN, and
+// all leftover fields are put into the last substring.
+func FieldsN(s string, maxN int) []string {
+	// First count the fields.
+	n := 0
+	inField := false
+	for _, rune := range s {
+		wasInField := inField
+		inField = !unicode.IsSpace(rune)
+		if inField && !wasInField {
+			n++
+		}
+	}
+	n = int(math.Min(float64(n), float64(maxN)))
+
+	// Now create them.
+	a := make([]string, n)
+	na := 0
+	fieldStart := -1 // Set to -1 when looking for start of field.
+	for i, rune := range s {
+		if unicode.IsSpace(rune) && na+1 < maxN {
+			if fieldStart >= 0 {
+				a[na] = s[fieldStart:i]
+				na++
+				fieldStart = -1
+			}
+		} else if fieldStart == -1 {
+			fieldStart = i
+		}
+	}
+	if fieldStart >= 0 { // Last field might end at EOF.
+		a[na] = s[fieldStart:]
+	}
+	return a
+}
diff --git a/utils_test.go b/utils_test.go
new file mode 100644
index 0000000..8252fce
--- /dev/null
+++ b/utils_test.go
@@ -0,0 +1,14 @@
+package jsh
+
+import "testing"
+
+func TestFieldsN(t *testing.T) {
+	testString := "Potatoes are the best strings for testing."
+	for i := 1; i <= 10; i++ {
+		fields := FieldsN(testString, i)
+		fieldsLength := len(fields)
+		if fieldsLength > i {
+			t.Errorf("Expected at most %d fields, got %d", i, fieldsLength)
+		}
+	}
+}