diff --git a/expr/container_test.go b/expr/container_test.go
new file mode 100644
index 00000000..31ec3d41
--- /dev/null
+++ b/expr/container_test.go
@@ -0,0 +1,96 @@
+package expr
+
+import (
+	"fmt"
+	"testing"
+)
+
+func TestContainerEvalName(t *testing.T) {
+	t.Parallel()
+	tests := []struct {
+		name, want string
+	}{
+		{name: "", want: "unnamed container"},
+		{name: "foo", want: `container "foo"`},
+	}
+	for _, tt := range tests {
+		tt := tt
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+			container := Container{
+				Element: &Element{
+					Name: tt.name,
+				},
+			}
+			if got := container.EvalName(); got != tt.want {
+				t.Errorf("got %s, want %s", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestContainerFinalize(t *testing.T) {
+	t.Parallel()
+	container := Container{
+		Element: &Element{
+			Name: "foo",
+		},
+	}
+	tests := []struct {
+		pre  func()
+		want string
+	}{
+		{want: ""},
+		{pre: func() { container.Tags = "foo" }, want: "foo"},
+		{pre: func() { container.Finalize() }, want: "Element,Container,foo"},
+	}
+	for i, tt := range tests {
+		tt := tt
+		t.Run(fmt.Sprint(i), func(t *testing.T) {
+			if tt.pre != nil {
+				tt.pre()
+			}
+			if got := container.Tags; got != tt.want {
+				t.Errorf("got %s, want %s", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestContainersElements(t *testing.T) {
+	t.Parallel()
+	containers := Containers{
+		{Element: &Element{Name: "foo"}},
+		{Element: &Element{Name: "bar"}},
+		{Element: &Element{Name: "baz"}},
+	}
+	if got := containers.Elements(); len(got) != len(containers) {
+		t.Errorf("got %d, want %d", len(got), len(containers))
+	}
+}
+
+func TestContainerComponent(t *testing.T) {
+	t.Parallel()
+	container := Container{
+		Components: Components{
+			{Element: &Element{Name: "foo"}},
+			{Element: &Element{Name: "bar"}},
+			{Element: &Element{Name: "baz"}},
+		},
+	}
+	tests := []struct {
+		name string
+		want *Component
+	}{
+		{name: "thud", want: nil},
+		{name: "bar", want: container.Components[1]},
+	}
+	for i, tt := range tests {
+		tt := tt
+		t.Run(fmt.Sprint(i), func(t *testing.T) {
+			if got := container.Component(tt.name); got != tt.want {
+				t.Errorf("got %#v, want %#v", got.Element, tt.want.Element)
+			}
+		})
+	}
+}