FShell Query Language (FQL)

[Google Scholar]

Notes: SV competition
Papers: holzer:cav:2008, holzer:hvc:2010

FQL is a query language for describing code coverage criteria. It consists of

  • structural constraints specified as path automata
  • quality constraints such as
    • block coverage
    • condition coverage
    • predicate coverage

The syntax of FQL is defined in holzer:hvc:2010. An FQL spec has the form

in G cover C passing P


  • “in G” and “passing P” are optional
  • G is a filter functon
    • “@FUNC()" ("@CALL" in later work)
    • “@CONDITIONEDGE” (“@DECISIONEDGE” in later work)
  • C is a coverage specification
    • A regexp like syntax
      • line specifications @4, @7, etc.
      • conditions “{ x == 42 }”, etc.
      • wildcards “ID”
      • quoted regexps
      • Normal regexp syntax: “.”, “”, “+”, “^” and “$” (“” can only occur inside quotes)
    • Which are used in
      • edges using “EDGES(regex)”
      • nodes (i.e., statements) using “NODES(regex)”
      • paths using “PATHS(T, k)” where “T” is a filter function and “k” is a bound on how many times “T” appears.
  • P is a “passing clause”: a path pattern that every test case must satisfy
    • For example, “^NOT(@CALL(unimplemented))*$”
    • For example, “^(ID.{x >= 0})*$” specifies tests where x never becomes negative.

The syntax “in @FUNC(foo) cover EDGES(@DEF(x))” is equivalent to “cover EDGES(COMPOSE(@DEF(x), @FUNC(foo)))”.


  • ”->” == “.ID*”

Software Verification Competition (SV-COMP), Software Testing Competition (Test-Comp)

  • TestCov: Robust test-suite execution and coverage measurement [beyer:ase:2019]
  • Software verification: Testing vs. model checking [beyer:hvc:2017]
  • FShell: Systematic test case generation for dynamic analysis and measurement [holzer:cav:2008]
  • An introduction to test specification in FQL [holzer:hvc:2010]