Stub out tcell.NewScreen so tests can pass headless.

.travis.yml

@@ -17,4 +17,4 @@ after_success:
         - ./internal/scripts/coverage.sh
 env:
   global:
-  - CGO_ENABLED=0
+        - CGO_ENABLED=0

CHANGELOG.md

@@ -9,6 +9,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [0.12.0] - 10-Apr-2020
 
+### Fixed
+
+- the `tcell` unit test can now pass in headless mode (when TERM="") which
+  happens under bazel.
+
 ### Added
 
 - Migrating to [Go modules](https://blog.golang.org/using-go-modules).

terminal/tcell/tcell.go

@@ -16,6 +16,7 @@ package tcell
 
 import (
 	"context"
+	"fmt"
 	"image"
 
 	"github.com/gdamore/tcell"
@@ -79,11 +80,14 @@ type Terminal struct {
 	clearStyle *cell.Options
 }
 
+// tcellNewScreen can be overridden from tests.
+var tcellNewScreen = tcell.NewScreen
+
 // newTerminal creates the terminal and applies the options.
 func newTerminal(opts ...Option) (*Terminal, error) {
-	screen, err := tcell.NewScreen()
+	screen, err := tcellNewScreen()
 	if err != nil {
-		return nil, err
+		return nil, fmt.Errorf("tcell.NewScreen => %v", err)
 	}
 
 	t := &Terminal{

terminal/tcell/tcell_test.go

@@ -17,6 +17,7 @@ package tcell
 import (
 	"testing"
 
+	"github.com/gdamore/tcell"
 	"github.com/kylelemons/godebug/pretty"
 	"github.com/mum4k/termdash/cell"
 	"github.com/mum4k/termdash/terminal/terminalapi"
@@ -45,11 +46,13 @@ func TestNewTerminalColorMode(t *testing.T) {
 		},
 	}
 
+	tcellNewScreen = func() (tcell.Screen, error) { return nil, nil }
 	for _, tc := range tests {
 		t.Run(tc.desc, func(t *testing.T) {
 			got, err := newTerminal(tc.opts...)
 			if err != nil {
 				t.Errorf("newTerminal => unexpected error:\n%v", err)
+				return
 			}
 
 			// Ignore these fields.
@@ -96,11 +99,13 @@ func TestNewTerminalClearStyle(t *testing.T) {
 		},
 	}
 
+	tcellNewScreen = func() (tcell.Screen, error) { return nil, nil }
 	for _, tc := range tests {
 		t.Run(tc.desc, func(t *testing.T) {
 			got, err := newTerminal(tc.opts...)
 			if err != nil {
 				t.Errorf("newTerminal => unexpected error:\n%v", err)
+				return
 			}
 
 			// Ignore these fields.