Add spec coverage for base filter input form

Covers BaseFilterForm's shared row contract directly via a throwaway
concrete subclass: row data attributes, the operator select with its
data-no-value branch, label targeting, hidden-when-inactive, the delete
button, hiding the operator select for a boolean filter, and the
abstract add_operand raising SubclassResponsibilityError.

spec/forms/filters/inputs/base_filter_form_spec.rb

@@ -0,0 +1,129 @@
+# frozen_string_literal: true
+
+#-- copyright
+# OpenProject is an open source project management software.
+# Copyright (C) the OpenProject GmbH
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License version 3.
+#
+# OpenProject is a fork of ChiliProject, which is a fork of Redmine. The copyright follows:
+# Copyright (C) 2006-2013 Jean-Philippe Lang
+# Copyright (C) 2010-2013 the ChiliProject Team
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License
+# as published by the Free Software Foundation; either version 2
+# of the License, or (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+#
+# See COPYRIGHT and LICENSE files for more details.
+#++
+
+require "spec_helper"
+
+RSpec.describe Filters::Inputs::BaseFilterForm, type: :forms do
+  include ViewComponent::TestHelpers
+
+  let!(:date_field) { create(:user_custom_field, field_format: "date") }
+  let(:query) { UserQuery.new }
+  let(:filter) { query.available_advanced_filters.find { |af| af.name == :"cf_#{date_field.id}" } }
+  let(:active) { true }
+
+  # Concrete subclass so the abstract base can be rendered: BaseFilterForm#add_operand
+  # raises SubclassResponsibilityError, so every real subclass supplies an operand.
+  let(:form_class) do
+    Class.new(described_class) do
+      def add_operand(group)
+        group.text_field(name: operand_name, label: @filter.human_name)
+      end
+    end
+  end
+
+  def render_base_form(form_class: self.form_class, filter: self.filter, active: self.active)
+    render_in_view_context(form_class, filter, active) do |form_class, filter, active|
+      primer_form_with(url: "/test", method: :post) do |f|
+        render(form_class.new(f, filter:, additional_attributes: {}, active:))
+      end
+    end
+    page
+  end
+
+  subject(:rendered_form) { render_base_form }
+
+  it "renders the row group with filter data attributes" do
+    expect(rendered_form).to have_element "data-filter--filters-form-target": "filter",
+                                          "data-filter-name": filter.name.to_s,
+                                          "data-filter-type": filter.type.to_s
+  end
+
+  it "renders the operator select with the filter's operators" do
+    expect(rendered_form).to have_select "operator_#{filter.name}" do |select|
+      filter.available_operators.each do |op|
+        expect(select).to have_selector :option, text: op.human_name
+      end
+    end
+  end
+
+  it "marks value-less operators with data-no-value and leaves the rest untouched" do
+    select = rendered_form.find(:select, "operator_#{filter.name}", visible: :all)
+
+    filter.available_operators.each do |op|
+      option = select.find(:element, :option, value: op.symbol, visible: :all)
+
+      if op.requires_value?
+        expect(option["data-no-value"]).to be_nil
+      else
+        expect(option["data-no-value"]).to eq("true")
+      end
+    end
+  end
+
+  it "points the label at the operator select for a non-boolean filter" do
+    expect(rendered_form).to have_element :label,
+                                          text: filter.human_name,
+                                          for: "operator_#{filter.name}"
+  end
+
+  it "renders a delete button within the filter row" do
+    expect(rendered_form).to have_element "data-filter--filters-form-target": "filter" do |row|
+      expect(row).to have_element "tool-tip", text: I18n.t("button_delete")
+    end
+  end
+
+  context "when inactive" do
+    let(:active) { false }
+
+    it "hides the row" do
+      expect(rendered_form).to have_element "data-filter--filters-form-target": "filter",
+                                            "data-filter-name": filter.name.to_s,
+                                            hidden: "hidden",
+                                            visible: :all
+    end
+  end
+
+  context "with a boolean filter" do
+    let!(:bool_field) { create(:user_custom_field, field_format: "bool") }
+    let(:filter) { query.available_advanced_filters.find { |af| af.name == :"cf_#{bool_field.id}" } }
+
+    it "hides the operator select" do
+      expect(rendered_form).to have_select "operator_#{filter.name}", visible: :hidden
+    end
+  end
+
+  context "when add_operand is not overridden" do
+    let(:form_class) { Class.new(described_class) }
+
+    it "raises SubclassResponsibilityError when rendered" do
+      expect { render_base_form }.to raise_error(SubclassResponsibilityError)
+    end
+  end
+end