What's New in Vedro v1.15

Vedro v1.15 brings cleaner scenario authoring, powerful reusable assertions, and richer reporting. Plus a handful of QoL (Quality of Life) upgrades that make everyday testing smoother.

Enhanced Scenario Decorator (Subject & Tags)

The @scenario decorator now supports custom subjects and inline tag assignment, making test organization more flexible and intuitive:

from vedro import scenario

@scenario("create user")
def _():
    ...

Attach tags inline:

from vedro import scenario

@scenario("update user", tags={"API"})
def _():
    ...

New @effect Decorator for Reusable Assertions

Introduce reusable test logic with the new @effect decorator, perfect for complex test suites with common validation patterns:

# ./effects/dir_was_created.py
from vedro import effect

@effect
def dir_was_created(d: Path):
    assert d.exists(), f"Directory not found: {d}"
    assert d.is_dir(), f"Path exists but is not a directory: {d}"

Use it in scenarios just like a tiny test helper:

# ./scenarios/export_user_data.py
from vedro import scenario, given, when, then
from effects.dir_was_created import dir_was_created

@scenario("export user data")
def _():
    with given:
        export_dir = Path("/tmp/user_exports")

    with when:
        # ... export logic ...

    with then:
        assert dir_was_created(export_dir)

Per-Scenario Seed Configuration (@seed) + Shorter Seed Format

Gain precise control over randomness at the scenario level:

Structured

from vedro import scenario, seed

@scenario[seed("value-123")]
def create_user():
    ...

Expressive

import vedro
from vedro import seed

@seed("value-123")
class Scenario(vedro.Scenario):
    subject = "create user"

Vedro v1.15 also adopts a more readable seed style:

# --seed rdx3-36ep6-2ijo
# 1 scenario, 1 passed, 0 failed, 0 skipped (0.00s)

Output Capture (stdout/stderr)

Capture and display stdout/stderr from scenarios and steps with the new --capture-output (-C) flag:

$ vedro run --capture-output

Tune visibility in RichReporter:

class RichReporter(rich_reporter.RichReporter):
    show_captured_output: bool = True
    show_captured_output_limit: int = 40  # Character limit for displayed output

Pre-run Preamble (Discovery Stats & Seed)

See what’s about to run before it runs:

• Discovered scenarios
• Scheduled to run
• Skipped (if any)

>> running: 2 of 6 scenarios (1 skipped, 3 ignored)
Scenarios
* 
 ✔ create user (0.00s)
 ...

Toggle via config:

class RichReporter(rich_reporter.RichReporter):
    show_discovery_stats: bool = False

Prefer seeing the seed upfront (not just at the end)? Enable the seed preamble:

class Seeder(seeder.Seeder):
    show_seed_preamble: bool = True

External plugins can add their own preamble sections to surface critical info early.

Paths With Line Numbers

--show-paths now includes line numbers:

$ vedro run --show-paths

Scenarios
* 
 ✔ update user (0.00s)
   |> scenarios/update_user.py:5
 
# --seed 35ee-zgkjp-wlgo
# 1 scenario, 1 passed, 0 failed, 0 skipped (0.00s)

info

Many terminals/IDEs support cmd/ctrl+click to jump straight to the definition.

Even better, you can run by line:

$ vedro run scenarios/update_user.py:5

Simpler Worker Slicing (--slice N/M)

No more pairing two flags, pick a single slice with one arg:

Slicer:
  --slicer-total SLICER_TOTAL    Total number of workers
  --slicer-index SLICER_INDEX    Index of the current worker (zero based)
  --slice N/M                    Specify slice as <index>/<total> (index starts at 1).
                                 Mutually exclusive with the two flags above.

Example:

$ vedro run --slice 2/5

Color Output Control

Turn off ANSI colors if your environment/CI prefers plain text:

$ vedro run --no-color

Or via config:

class RichReporter(rich_reporter.RichReporter):
    no_color: bool = True

JSON Reporter (Machine-Readable Events)

A new JsonReporter streams structured events: perfect for IDE integrations, AI agents, MCP, or custom dashboards:

$ vedro run -r json

Sample event (formatted):

{
    "event": "scenario_reported",
    "timestamp": 1758743760292,
    "scenario": {
        "id": "scenarios/export_user_data.py::export_user_data",
        "subject": "export user data",
        "path": "/app/scenarios/export_user_data.py",
        "lineno": 6,
        "status": "FAILED",
        "elapsed": 0,
        "skip_reason": null
    },
    "steps": [
        {"name": "given", "status": "PASSED", "elapsed": 0, "error": null},
        {"name": "when", "status": "PASSED", "elapsed": 0, "error": null},
        {
            "name": "then ",
            "status": "FAILED",
            "elapsed": 0,
            "error": {
                "type": "AssertionError",
                "message": "Directory not found: /tmp/user_exports",
                "file": "/app/effects/dir_was_created.py",
                "lineno": 8
            }
        }
    ]
}

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