add test coverage for panics

ocis-pkg/os/os_test.go

@@ -13,9 +13,11 @@ func Test_mustUserConfigDir(t *testing.T) {
 		extension string
 	}
 	tests := []struct {
-		name string
-		args args
-		want string
+		name      string
+		args      args
+		want      string
+		resetHome bool
+		panic     bool
 	}{
 		{
 			name: "fetch the default config location for the current user",
@@ -25,12 +27,36 @@ func Test_mustUserConfigDir(t *testing.T) {
 			},
 			want: filepath.Join(configDir, "ocis", "testing"),
 		},
+		{
+			name: "location cannot be determined becahse $HOME is not set",
+			args: args{
+				prefix:    "ocis",
+				extension: "testing",
+			},
+			want:      filepath.Join(configDir, "ocis", "testing"),
+			resetHome: true,
+			panic:     true,
+		},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
+
+			if tt.resetHome {
+				if err := os.Setenv("HOME", ""); err != nil {
+					t.Error(err)
+				}
+			}
+
+			defer func() {
+				if r := recover(); r != nil && !tt.panic {
+					t.Errorf("should have panicked!")
+				}
+			}()
+
 			if got := MustUserConfigDir(tt.args.prefix, tt.args.extension); got != tt.want {
 				t.Errorf("MustUserConfigDir() = %v, want %v", got, tt.want)
 			}
+
 		})
 	}
 }