diff --git a/src/mnemonicode/mnemonicode_test.go b/src/mnemonicode/mnemonicode_test.go
new file mode 100644
index 00000000..31301f1e
--- /dev/null
+++ b/src/mnemonicode/mnemonicode_test.go
@@ -0,0 +1,171 @@
+package mnemonicode
+
+import (
+	"testing"
+)
+
+func TestWordsRequired(t *testing.T) {
+	tests := []struct {
+		name   string
+		length int
+		want   int
+	}{
+		{"empty", 0, 0},
+		{"1 byte", 1, 1},
+		{"2 bytes", 2, 2},
+		{"3 bytes", 3, 3},
+		{"4 bytes", 4, 3},
+		{"5 bytes", 5, 4},
+		{"8 bytes", 8, 6},
+		{"12 bytes", 12, 9},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := WordsRequired(tt.length); got != tt.want {
+				t.Errorf("WordsRequired(%d) = %d, want %d", tt.length, got, tt.want)
+			}
+		})
+	}
+}
+
+func TestEncodeWordList(t *testing.T) {
+	tests := []struct {
+		name string
+		dst  []string
+		src  []byte
+		want int
+	}{
+		{
+			name: "empty input",
+			dst:  []string{},
+			src:  []byte{},
+			want: 0,
+		},
+		{
+			name: "single byte",
+			dst:  []string{},
+			src:  []byte{0x01},
+			want: 1,
+		},
+		{
+			name: "two bytes",
+			dst:  []string{},
+			src:  []byte{0x01, 0x02},
+			want: 2,
+		},
+		{
+			name: "three bytes",
+			dst:  []string{},
+			src:  []byte{0x01, 0x02, 0x03},
+			want: 3,
+		},
+		{
+			name: "four bytes",
+			dst:  []string{},
+			src:  []byte{0x01, 0x02, 0x03, 0x04},
+			want: 3,
+		},
+		{
+			name: "eight bytes",
+			dst:  []string{},
+			src:  []byte{0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08},
+			want: 6,
+		},
+		{
+			name: "with existing dst",
+			dst:  []string{"existing"},
+			src:  []byte{0x01},
+			want: 2,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result := EncodeWordList(tt.dst, tt.src)
+			if len(result) != tt.want {
+				t.Errorf("EncodeWordList() returned %d words, want %d", len(result), tt.want)
+			}
+			
+			// Check that all words are valid
+			for i, word := range result {
+				if word == "" {
+					t.Errorf("EncodeWordList() returned empty word at index %d", i)
+				}
+			}
+		})
+	}
+}
+
+func TestEncodeWordListConsistency(t *testing.T) {
+	input := []byte{0x12, 0x34, 0x56, 0x78}
+	
+	// Encode twice with empty dst
+	result1 := EncodeWordList([]string{}, input)
+	result2 := EncodeWordList([]string{}, input)
+	
+	if len(result1) != len(result2) {
+		t.Errorf("Inconsistent result lengths: %d vs %d", len(result1), len(result2))
+	}
+	
+	for i := range result1 {
+		if result1[i] != result2[i] {
+			t.Errorf("Inconsistent result at index %d: %s vs %s", i, result1[i], result2[i])
+		}
+	}
+}
+
+func TestEncodeWordListCapacityHandling(t *testing.T) {
+	// Test with dst that has sufficient capacity
+	dst := make([]string, 1, 10)
+	dst[0] = "existing"
+	input := []byte{0x01, 0x02}
+	
+	result := EncodeWordList(dst, input)
+	
+	if len(result) != 3 { // 1 existing + 2 new
+		t.Errorf("Expected 3 words, got %d", len(result))
+	}
+	
+	if result[0] != "existing" {
+		t.Errorf("Expected first word to be 'existing', got %s", result[0])
+	}
+}
+
+func TestEncodeWordListBoundaryValues(t *testing.T) {
+	tests := []struct {
+		name string
+		src  []byte
+	}{
+		{"max single byte", []byte{0xFF}},
+		{"max two bytes", []byte{0xFF, 0xFF}},
+		{"max three bytes", []byte{0xFF, 0xFF, 0xFF}},
+		{"max four bytes", []byte{0xFF, 0xFF, 0xFF, 0xFF}},
+		{"all zeros", []byte{0x00, 0x00, 0x00, 0x00}},
+	}
+	
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result := EncodeWordList([]string{}, tt.src)
+			expectedLen := WordsRequired(len(tt.src))
+			
+			if len(result) != expectedLen {
+				t.Errorf("Expected %d words, got %d", expectedLen, len(result))
+			}
+			
+			// Ensure all words are from the WordList
+			for _, word := range result {
+				found := false
+				for _, validWord := range WordList {
+					if word == validWord {
+						found = true
+						break
+					}
+				}
+				if !found {
+					t.Errorf("Invalid word generated: %s", word)
+				}
+			}
+		})
+	}
+}
\ No newline at end of file
diff --git a/src/models/models_test.go b/src/models/models_test.go
new file mode 100644
index 00000000..d4aaca91
--- /dev/null
+++ b/src/models/models_test.go
@@ -0,0 +1,179 @@
+package models
+
+import (
+	"net"
+	"strings"
+	"testing"
+	"time"
+)
+
+func TestConstants(t *testing.T) {
+	if TCP_BUFFER_SIZE != 1024*64 {
+		t.Errorf("TCP_BUFFER_SIZE = %d, want %d", TCP_BUFFER_SIZE, 1024*64)
+	}
+
+	if DEFAULT_PORT != "9009" {
+		t.Errorf("DEFAULT_PORT = %s, want %s", DEFAULT_PORT, "9009")
+	}
+
+	if DEFAULT_PASSPHRASE != "pass123" {
+		t.Errorf("DEFAULT_PASSPHRASE = %s, want %s", DEFAULT_PASSPHRASE, "pass123")
+	}
+}
+
+func TestPublicDNSServers(t *testing.T) {
+	if len(publicDNS) == 0 {
+		t.Error("publicDNS list should not be empty")
+	}
+
+	// Check that we have both IPv4 and IPv6 servers
+	hasIPv4 := false
+	hasIPv6 := false
+
+	for _, dns := range publicDNS {
+		if strings.Contains(dns, "[") {
+			hasIPv6 = true
+		} else {
+			hasIPv4 = true
+		}
+	}
+
+	if !hasIPv4 {
+		t.Error("publicDNS should contain IPv4 servers")
+	}
+
+	if !hasIPv6 {
+		t.Error("publicDNS should contain IPv6 servers")
+	}
+
+	// Verify known DNS servers are present
+	expectedServers := []string{
+		"1.1.1.1",        // Cloudflare
+		"8.8.8.8",        // Google
+		"9.9.9.9",        // Quad9
+		"208.67.220.220", // OpenDNS
+	}
+
+	for _, expected := range expectedServers {
+		found := false
+		for _, dns := range publicDNS {
+			if dns == expected {
+				found = true
+				break
+			}
+		}
+		if !found {
+			t.Errorf("Expected DNS server %s not found in publicDNS", expected)
+		}
+	}
+}
+
+func TestLocalLookupIP(t *testing.T) {
+	tests := []struct {
+		name    string
+		address string
+		wantErr bool
+	}{
+		{
+			name:    "localhost",
+			address: "localhost",
+			wantErr: false,
+		},
+		{
+			name:    "invalid hostname",
+			address: "this-hostname-should-not-exist-12345",
+			wantErr: true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			ip, err := localLookupIP(tt.address)
+
+			if (err != nil) != tt.wantErr {
+				t.Errorf("localLookupIP() error = %v, wantErr %v", err, tt.wantErr)
+				return
+			}
+
+			if !tt.wantErr && ip == "" {
+				t.Error("localLookupIP() returned empty IP for valid hostname")
+			}
+
+			if !tt.wantErr {
+				// Verify it's a valid IP address
+				if net.ParseIP(ip) == nil {
+					t.Errorf("localLookupIP() returned invalid IP: %s", ip)
+				}
+			}
+		})
+	}
+}
+
+func TestRemoteLookupIPTimeout(t *testing.T) {
+	// Test with an invalid DNS server that should timeout
+	start := time.Now()
+	_, err := remoteLookupIP("example.com", "192.0.2.1")
+	duration := time.Since(start)
+
+	// Should timeout within reasonable time (we set 500ms timeout)
+	if duration > time.Second {
+		t.Errorf("remoteLookupIP took too long: %v", duration)
+	}
+
+	if err == nil {
+		t.Error("remoteLookupIP should have failed with invalid DNS server")
+	}
+}
+
+func TestLookupFunction(t *testing.T) {
+	// Test the main lookup function
+	tests := []struct {
+		name    string
+		address string
+		wantErr bool
+	}{
+		{
+			name:    "localhost",
+			address: "localhost",
+			wantErr: false,
+		},
+		{
+			name:    "invalid hostname",
+			address: "this-hostname-should-definitely-not-exist-98765",
+			wantErr: true,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			ip, err := lookup(tt.address)
+
+			if (err != nil) != tt.wantErr {
+				t.Errorf("lookup() error = %v, wantErr %v", err, tt.wantErr)
+				return
+			}
+
+			if !tt.wantErr && ip == "" {
+				t.Error("lookup() returned empty IP for valid hostname")
+			}
+
+			if !tt.wantErr {
+				// Verify it's a valid IP address
+				if net.ParseIP(ip) == nil {
+					t.Errorf("lookup() returned invalid IP: %s", ip)
+				}
+			}
+		})
+	}
+}
+
+func TestGetConfigFile(t *testing.T) {
+	fname, err := getConfigFile(false)
+	if err != nil {
+		t.Skip("Could not get config directory")
+	}
+
+	if !strings.HasSuffix(fname, "internal-dns") {
+		t.Errorf("Expected config file to end with 'internal-dns', got %s", fname)
+	}
+}