Refactor snippet and remove tests to focus on user behavior

Problem

The snippet and remove test suites contain tests that verify implementation details rather than user-facing behavior, particularly around buffer operations and deletion workflows.

Snippet Tests Issues (tests/zk-extras/snippet_spec.lua)

1. Implementation detail testing (lines 312-336)

Current: Tests insertion "at middle of line" with specific cursor positioning

vim.api.nvim_win_set_cursor(0, {1, 7}) -- After "before "
assert.is_true(line:match("before") ~= nil)
assert.is_true(line:match("INSERTED") ~= nil)

Issue: Tests exact buffer manipulation, not behavior

Should test:

• "Snippet insertion preserves surrounding content"
• "Cursor is positioned after inserted snippet"
• Don't verify exact character positions

2. Buffer state testing (lines 338-363)

Current: Tests snippet "with only whitespace"

vim.fn.writefile({"   ", "  "}, snippet_dir .. "/whitespace.md")
assert.is_true(#lines > 1) -- Multi-line snippet

Should test:

• User-visible behavior: "Empty-looking snippets are handled gracefully"
• Error messaging if snippets should not be whitespace-only
• Don't test buffer line counts

3. Good test that should be model (lines 281-309)

This is excellent: Tests undo history preservation - actual user behavior!

Remove Tests Issues (tests/zk-extras/remove_spec.lua)

1. Deletion flow testing (lines 137-170)

Current: Tests exact fallback order: trash → hard delete

local orig_move = utils.move_to_trash
utils.move_to_trash = function() return false end
-- Test hard delete is called

Issue: Tests implementation sequence, not requirement

Should test:

describe("note deletion", function()
  it("successfully deletes note using available method", function()
    -- Verify note is gone
    -- Verify user notified of method used
    -- Don't care about order of attempts

2. Missing workflow tests

Need tests for:

• Deleting note open in multiple buffers
• Deleting currently edited note vs other note
• Deletion when file is externally modified
• Cancellation at various points in workflow
• State after deletion failure (buffer state, file state)

3. Remove_pick issues (lines 203-441)

Good behavioral tests:

• Lines 225-244: Error when .zk not found ✓
• Lines 390-415: No notes found handling ✓

Implementation detail tests:

• Lines 417-440: Tests .zk exclusion logic
  • Should test: "Only user notes are shown in picker"
  • Not: "Files matching /%.zk/ pattern are excluded"

Recommended Changes

1. Rewrite snippet tests

describe("snippet insertion", function()
  it("preserves existing buffer content", function()
    -- Setup buffer with content
    -- Insert snippet
    -- Verify original content intact
    -- Verify snippet added
    -- Don't check exact positions

  it("respects cursor position", function()
    -- Place cursor
    -- Insert snippet
    -- Verify snippet at logical position
    -- Don't verify exact API calls

  it("handles empty snippets gracefully", function()
    -- Test user experience, not implementation

2. Rewrite deletion tests

describe("note deletion workflow", function()
  it("successfully removes note from filesystem", function()
    -- Create note
    // Delete via command
    // Verify file gone
    // Verify buffers cleaned up
    // Don't test trash vs hard delete order

  it("handles concurrent buffer access correctly", function()
    // Open note in multiple windows
    // Delete note
    // Verify all buffers handled correctly

  it("recovers cleanly from deletion failures", function()
    // Mock filesystem error
    // Verify user gets helpful error
    // Verify no partial state

3. Add missing integration tests

describe("snippet to deletion workflow", function()
  it("allows deletion of note with inserted snippets", function()
    // Create note
    // Insert snippet
    // Modify content
    // Delete note
    // Verify complete cleanup

Success Criteria

• All tests verify user-visible behavior
• Implementation can change without breaking tests
• Edge cases are covered (multi-buffer, concurrent access)
• Error recovery is tested
• User workflow journeys are tested end-to-end

References

• tests/zk-extras/snippet_spec.lua lines 281-363
• tests/zk-extras/remove_spec.lua lines 137-441
• lua/zk-extras/snippet.lua
• lua/zk-extras/remove.lua