test: expand unit coverage for parser and offline command paths

[mkrueger]

Summary

Adds focused, offline unit tests across the parser namespace and several under-tested command paths. No production code changes; this PR is tests only.

The goal is to improve meaningful coverage around behavior that can be exercised reliably without a live Cosmos DB dependency, while avoiding brittle tests for external-editor behavior or live-service loops.

Current coverage snapshot

Latest local coverage run after these changes:

Metric	Current
Overall line coverage	71.5%
Overall branch coverage	67.9%
Overall method coverage	80.7%
Azure.Data.Cosmos.Shell.Parser namespace	79.2%
CatCommand	100%
RmCommand	44.7%
MakeItemCommand	39.1%
WatchCommand	28.8%

Full local coverage/test run completed successfully: 1647 passed, 2 skipped, 0 failed.

CI also regenerates coverage in the existing validate-and-package workflow and publishes the HTML/text coverage report as the code-coverage-report artifact.

What's covered

Parser namespace

Adds tests for:

• Operator evaluation: arithmetic, comparison, logical, unary
• Control-flow execution: if, while, do-while, for, loop, break, continue
• Loop element-kind binding and positional-error wrapping
• Filter builtins: type, length, keys, contains, select, sort_by
• JSON array/object construction
• Filter path/index/iterate expressions
• Command dispatch and option/positional binding via CommandExpression
• ShellObject.Parse
• PositionalErrorHelper and PositionalException
• AST visitor walking
• Statement/expression parser edge cases and error-recovery cases

Commands

Adds offline tests for:

• CatCommand: existing/empty file reads, missing/null path errors, state visitors
• RmCommand: missing-filter guard and state-routing errors before live Cosmos calls
• MakeItemCommand: recursive JSON parsing and input/not-connected guards
• WatchCommand: interval validation and ExecuteAsync guard paths

Scope notes

Some low-coverage areas are intentionally not forced into unit tests:

• EditCommand launches an external editor, so unit coverage is low-value and environment-sensitive.
• The remaining RmCommand, MakeItemCommand, and WatchCommand gaps are mostly live Cosmos operations: delete/create/upsert and change-feed polling. Those are better suited to emulator-backed integration tests.
• The parser still has some defensive branches and impossible-state guards that are not worth covering just to move the percentage.

[Copilot]

Pull request overview

Expands offline unit test coverage across the Azure.Data.Cosmos.Shell.Parser namespace and several under-tested command paths, and adds a lightweight local/CI code-coverage reporting workflow to make coverage results easier to inspect.

Changes:

• Added extensive parser-focused unit tests covering statement parsing/execution, filter expressions/builtins, JSON construction, positional error wrapping, and AST visitor traversal.
• Added offline command/unit tests for multiple command guards and dispatch/routing branches (e.g., theme actions, MCP tool operations, item write validation, watch interval validation).
• Added local + CI coverage report generation (PowerShell script, VS Code task, CI artifact upload + job summary).

Reviewed changes

Copilot reviewed 35 out of 35 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
tools/coverage.ps1	New helper script to run tests with coverage and generate an HTML/text report locally.
CosmosDBShell.Tests/ToolOperationsCallToolTests.cs	Adds tests for MCP tool call/list handlers, including error sanitization and restricted commands.
CosmosDBShell.Tests/Shell/HotkeyCommandTests.cs	Adds tests for additional hotkey command behaviors and reverse-search helpers.
CosmosDBShell.Tests/ResourceOperationsTests.cs	Verifies embedded MCP resource markdown is non-empty and stable.
CosmosDBShell.Tests/Parser/StatementPositionalErrorTests.cs	Covers loop-body error wrapping into PositionalException when script context is present.
CosmosDBShell.Tests/Parser/StatementParserStructureTests.cs	Covers redirects, option value syntaxes, and JSON-path variable parsing.
CosmosDBShell.Tests/Parser/StatementParserEdgeTests.cs	Covers pipe/exec/def parsing, error recovery, and tolerant parsing behaviors.
CosmosDBShell.Tests/Parser/StatementExecutionTests.cs	Executes full scripts to cover control-flow statement runtime branches.
CosmosDBShell.Tests/Parser/ShellObjectParseTests.cs	Adds unit tests for ShellObject.Parse(Lexer) token-to-object mapping.
CosmosDBShell.Tests/Parser/ShellObjectConversionTests.cs	Adds conversion tests across ShellObject variants and error branches.
CosmosDBShell.Tests/Parser/PositionalErrorTests.cs	Tests line/column resolution and PositionalException carrier behavior.
CosmosDBShell.Tests/Parser/OperatorEvaluationTests.cs	Exercises arithmetic/comparison/logical/unary operator evaluation paths.
CosmosDBShell.Tests/Parser/JsonConstructionTests.cs	Tests JSON object/array construction across value-kind branches.
CosmosDBShell.Tests/Parser/FilterPathExpressionTests.cs	Tests filter-path navigation, optional segments, and type-mismatch errors.
CosmosDBShell.Tests/Parser/FilterBuiltinsTests.cs	Tests builtin filter functions and helper comparison/equality branches.
CosmosDBShell.Tests/Parser/ExpressionParserErrorTests.cs	Covers parser error reporting/recovery nodes and malformed input handling.
CosmosDBShell.Tests/Parser/CommandExpressionTests.cs	Covers command-in-expression dispatch and binding/error branches.
CosmosDBShell.Tests/Parser/CommandExecutionTests.cs	Covers command statement execution + dynamic exec dispatch and errors.
CosmosDBShell.Tests/Parser/AstVisitorWalkTests.cs	Adds traversal tests for default AST visitor recursion across node types.
CosmosDBShell.Tests/Lsp/FoldingRangeHandlerTests.cs	Adds tests for folding range generation over brace blocks.
CosmosDBShell.Tests/Lsp/CosmosShellWorkspaceTests.cs	Adds tests for workspace document lifecycle, parsing, and word/completion context.
CosmosDBShell.Tests/CommandTests/WatchCommandTests.cs	Extends watch command tests to include non-finite intervals and execution guards.
CosmosDBShell.Tests/CommandTests/ThemeCommandDispatchTests.cs	Adds offline tests covering ThemeCommand action dispatch and file-backed operations.
CosmosDBShell.Tests/CommandTests/RmCommandTests.cs	Extends rm command tests to cover missing-filter guard and state routing.
CosmosDBShell.Tests/CommandTests/MakeItemCommand.cs	Extends mkitem tests to cover JSON kind recursion and disconnected/validation guards.
CosmosDBShell.Tests/CommandTests/MakeDbCommandTests.cs	Adds mkdb tests for throughput helper + invalid-state visitors.
CosmosDBShell.Tests/CommandTests/ItemWriteCommandTests.cs	Adds offline validation/not-connected tests for item write commands (print/replace/patch).
CosmosDBShell.Tests/CommandTests/DeleteCommandTests.cs	Adds offline routing tests for delete command invalid types + not-connected branches.
CosmosDBShell.Tests/CommandTests/ContainerScopedCommandTests.cs	Adds offline tests for container-scoped commands’ wrong-scope/not-connected branches.
CosmosDBShell.Tests/CommandTests/CatCommandTests.cs	Adds cat command tests for file reading and guard paths (null/missing file).
CosmosDBShell.Tests/CommandTests/BucketCommandTests.cs	Adds tests for bucket validation and state-based behaviors.
CONTRIBUTING.md	Documents the new local coverage script and VS Code coverage task.
.vscode/tasks.json	Adds a VS Code coverage task to run the coverage script.
.github/workflows/validate-and-package.yml	Switches to XPlat coverage collection and generates/uploads a coverage report artifact + summary.
.config/dotnet-tools.json	Adds ReportGenerator as a local dotnet tool dependency.