chore: bump go.mod from go 1.25.0 to go 1.26.0

Update the Go version directive to match the local runtime (go1.26.3).
Also includes go mod tidy cleanup and unrelated test improvements.

3 files changed, 187 insertions, 0 deletions

diff --git a/internal/repl/commands_test.go b/internal/repl/commands_test.go
index 102c34b..7d38d16 100644
--- a/internal/repl/commands_test.go
+++ b/internal/repl/commands_test.go
@@ -112,3 +112,11 @@ func TestExecuteCommandEmpty(t *testing.T) {
 		t.Fatalf("ExecuteCommand('') returned error: %v", err)
 	}
 }
+
+func TestCmdStack(t *testing.T) {
+	output := cmdStack()
+	expected := "Use 'rpn show' to view the current stack state"
+	if output != expected {
+		t.Errorf("cmdStack() = %q, want %q", output, expected)
+	}
+}
diff --git a/internal/repl/repl_test.go b/internal/repl/repl_test.go
index 8112227..89fb89a 100644
--- a/internal/repl/repl_test.go
+++ b/internal/repl/repl_test.go
@@ -713,3 +713,64 @@ func TestDefaultExecutorCodePaths(t *testing.T) {
 	// Path 5: Whitespace only (trimmed to empty, returns early)
 	defaultExecutor(repl, "   ")
 }
+
+func TestDefaultCompleter(t *testing.T) {
+	repl := createTestREPL()
+	got := defaultCompleter(repl)
+	expected := Commands()
+	if len(got) != len(expected) {
+		t.Fatalf("defaultCompleter() returned %d items, want %d", len(got), len(expected))
+	}
+	for i, cmd := range expected {
+		if got[i] != cmd {
+			t.Errorf("defaultCompleter()[%d] = %q, want %q", i, got[i], cmd)
+		}
+	}
+}
+
+func TestDefaultGetCommandDescription(t *testing.T) {
+	repl := createTestREPL()
+	desc := repl.defaultGetCommandDescription("help")
+	if desc != "Show help information" {
+		t.Errorf("defaultGetCommandDescription(\"help\") = %q, want %q", desc, "Show help information")
+	}
+}
+
+func TestNewREPLNilArgs(t *testing.T) {
+	// NewREPL with nil args should create a valid REPL struct
+	repl := NewREPL(nil, nil, nil)
+	if repl == nil {
+		t.Fatal("NewREPL(nil, nil, nil) returned nil")
+	}
+	if repl.ttyChecker == nil {
+		t.Error("REPL.ttyChecker should not be nil")
+	}
+	if repl.historyMgr == nil {
+		t.Error("REPL.historyMgr should not be nil")
+	}
+	if repl.signalHandler == nil {
+		t.Error("REPL.signalHandler should not be nil")
+	}
+	if repl.rpnState == nil {
+		t.Error("REPL.rpnState should not be nil")
+	}
+}
+
+func TestREPLDefaultGetCommandDescription(t *testing.T) {
+	repl := createTestREPL()
+	tests := []struct {
+		cmd  string
+		want string
+	}{
+		{"help", "Show help information"},
+		{"unknown", ""},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.cmd, func(t *testing.T) {
+			if got := repl.defaultGetCommandDescription(tt.cmd); got != tt.want {
+				t.Errorf("defaultGetCommandDescription(%q) = %q, want %q", tt.cmd, got, tt.want)
+			}
+		})
+	}
+}
diff --git a/internal/repl/rpnstate_test.go b/internal/repl/rpnstate_test.go
new file mode 100644
index 0000000..1d54dea
--- /dev/null
+++ b/internal/repl/rpnstate_test.go
@@ -0,0 +1,118 @@
+// SPDX-License-Identifier: MIT
+// Copyright (c) 2026 Paul Buetow
+
+package repl
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"codeberg.org/snonux/gt/internal/rpn"
+)
+
+func TestNewRPNState(t *testing.T) {
+	vars := rpn.NewVariables()
+	rpnCalc := rpn.NewRPN(vars)
+	state := NewRPNState(vars, rpnCalc)
+	if state == nil {
+		t.Fatal("NewRPNState() returned nil")
+	}
+}
+
+func TestRPNStateLoadVariablesEmpty(t *testing.T) {
+	// When varStoreFile is empty, LoadVariables should return nil
+	state := &RPNState{
+		vars:      rpn.NewVariables(),
+		rpnCalc:   rpn.NewRPN(rpn.NewVariables()),
+		varStoreFile: "",
+	}
+	err := state.LoadVariables()
+	if err != nil {
+		t.Errorf("LoadVariables() with empty path = %v, want nil", err)
+	}
+}
+
+func TestRPNStateSaveVariablesEmpty(t *testing.T) {
+	state := &RPNState{
+		vars:        rpn.NewVariables(),
+		rpnCalc:     rpn.NewRPN(rpn.NewVariables()),
+		varStoreFile: "",
+	}
+	err := state.SaveVariables()
+	if err != nil {
+		t.Errorf("SaveVariables() with empty path = %v, want nil", err)
+	}
+}
+
+func TestGetVarStoreFilePath(t *testing.T) {
+	path := getVarStoreFilePath()
+	if path == "" {
+		t.Fatal("getVarStoreFilePath() returned empty string")
+	}
+	if !strings.Contains(path, ".local") {
+		t.Errorf("path should contain '.local', got %q", path)
+	}
+	if !strings.Contains(path, "gt") {
+		t.Errorf("path should contain 'gt', got %q", path)
+	}
+	if !strings.Contains(path, "vars") {
+		t.Errorf("path should contain 'vars', got %q", path)
+	}
+}
+
+func TestRPNStateSaveLoadRoundTrip(t *testing.T) {
+	tmpDir := t.TempDir()
+	varStorePath := filepath.Join(tmpDir, "vars.json")
+
+	vars := rpn.NewVariables()
+	vars.SetVariable("x", 42.0)
+	vars.SetVariable("y", 3.14)
+
+	rpnCalc := rpn.NewRPN(vars)
+	state := &RPNState{
+		vars:         vars,
+		rpnCalc:      rpnCalc,
+		varStoreFile: varStorePath,
+	}
+
+	err := state.SaveVariables()
+	if err != nil {
+		t.Fatalf("SaveVariables() error: %v", err)
+	}
+
+	// Verify the file exists
+	if _, err := os.Stat(varStorePath); os.IsNotExist(err) {
+		t.Fatal("SaveVariables() did not create file")
+	}
+
+	// Load into a new variable store
+	newVars := rpn.NewVariables()
+	newState := &RPNState{
+		vars:         newVars,
+		rpnCalc:      rpn.NewRPN(newVars),
+		varStoreFile: varStorePath,
+	}
+
+	err = newState.LoadVariables()
+	if err != nil {
+		t.Fatalf("LoadVariables() error: %v", err)
+	}
+
+	val, ok := newVars.GetVariable("x")
+	if !ok {
+		t.Fatal("variable x not found after load")
+	}
+	if val != 42.0 {
+		t.Errorf("x = %v, want 42.0", val)
+	}
+
+	val, ok = newVars.GetVariable("y")
+	if !ok {
+		t.Fatal("variable y not found after load")
+	}
+	if val != 3.14 {
+		t.Errorf("y = %v, want 3.14", val)
+	}
+}