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Markus Schirp

person 18 connections

Creator of Mutant, the mutation-testing tool for Ruby. Ran a mutation-testing workshop at wroclove.rb 2019 and delivered the follow-up talk 'Mutant on steroids' the next day. Works as a consultant, using Mutant in incremental mode on commercial Ruby/Rails codebases. First encountered mutation testing while joining the DataMapper 2 team around the axiom relational-algebra engine, which used the Haskell tool Heckle — a logical predecessor to Mutant. Has a strict policy of not contributing broadly to open source because it is 'addictive like cocaine' and interferes with making a living; submits only bug-fix patches (without advertising Mutant) to libraries where he hits semantic weak spots. Krzywda credits him with the observation that 'Active Record has an infinite API' — once a model inherits from ActiveRecord::Base, its interface becomes effectively unbounded.

person Markus Schirp
attended
wroclove.rb 2019 event
Ran a mutation-testing workshop at wroclove.rb 2019, referenced by Krzywda during the talk.
person Markus Schirp
attended
wroclove.rb 2026 event
Spoke at the conference and ran the same day's mutation-testing workshop.
person Markus Schirp
authored
Mutant on steroids talk
Schirp is the speaker of 'Mutant on steroids'.
person Markus Schirp
authored
My core skill never was the typing talk
person Markus Schirp
authored
Setup and operation of mutation testing in agentic world talk
Ran this mutation-testing workshop earlier the same day as the talk.
person Markus Schirp
authored
Mutant tool
Schirp is the creator of Mutant.
person Markus Schirp
authored
Mutation testing workshop wroclove.rb 2019 talk
Schirp ran the pre-conference mutation-testing workshop.
person Markus Schirp
authored
Discipline Doesn't Scale talk
Schirp delivered this talk at wroclove.rb 2026.
person Markus Schirp
recommends
Mutation Testing concept
Argues every project should use mutation testing because human time is the most expensive resource.
person Markus Schirp
recommends
Incremental Mutation Testing concept
Recommends incremental mode as the way to adopt mutation testing on existing codebases.
person Markus Schirp
recommends
Haskell tool
Says he would always work in Haskell if he had no economic constraints.
person Markus Schirp
recommends
Rust tool
His practical greenfield default — '80% Haskell, easy sell'.
person Markus Schirp
related_to
Development with axioms talk
Schirp is Gamsjaeger's close friend and teammate and a key co-author of the axiom-driven process described in the talk.
person Martin Gamsjaeger
related_to
Markus Schirp person
Close friends and teammates on the same fully-remote team.
person Markus Schirp
works_on
Mutant tool
Mentions building Mutant and converting it to a commercial tool to keep it alive.
role: creator
person Markus Schirp
works_on
DataMapper 2 project
Schirp joined the DataMapper 2 team; this is where he first encountered mutation testing.
role: team member
person Markus Schirp
works_on
axiom project
Worked on the axiom relational-algebra engine sub-project of DataMapper 2.
person Markus Schirp
works_on
Axiom-Driven Development concept
Co-developer of the methodology with Gamsjaeger and Kubb.
role: co-author of the process

Provenance

Created
2026-04-17 16:17 seed
Last updated in
Mutant on steroids — Markus Schirp at wroclove.rb 2019 2026-04-17 17:53
Total updates
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