E81010: invalid placeholder syntax in expected output

What went wrong

An expected output file contains an invalid placeholder syntax. Placeholders use EK9 type names in double braces: {{TypeName}}

Worked examples

Compilable examples demonstrating this error and the correct fix:

• ek9 -q 208 (How do I test output containing dynamic values like dates...)
• ek9 -q 953 (How do @Test programs work with command-line arguments...)

Valid placeholders

Basic: {{String}}, {{Integer}}, {{Float}}, {{Boolean}}, {{Character}}, {{Bits}}
Time:  {{Date}}, {{Time}}, {{DateTime}}, {{Duration}}, {{Millisecond}}
Other: {{Money}}, {{Colour}}, {{Resolution}}, {{Dimension}}, {{RegEx}}, {{GUID}}

Common typos

{{UUID}} -> {{GUID}}, {{Color}} -> {{Colour}}, {{Int}} -> {{Integer}}
{{datetime}} -> {{DateTime}}, {{Timestamp}} -> {{DateTime}}
{{Long}}/{{Double}} -> {{Integer}}/{{Float}}

Example

expected_output.txt:
  Test started at: {{DateTime}}
  Items processed: {{Integer}}
  Status: OK                    // Literal - must match exactly

How to fix it

1. Use correct EK9 type name (case-sensitive)
2. Use {{String}} as catch-all if no specific type fits
3. Remove {{ }} for literal text matching

Examples

Every example is compiled by the EK9 compiler: the first fails exactly as captioned, the others fix it.

Fails with E81010: invalid placeholder syntax in expected output - reported by the test runner, not the compiler, when ek9 -t greeting.ek9 runs in this project.

bad/greeting.ek9

#!ek9
defines module error.e81010.bad

  defines function

    greeting() as pure
      -> name as String
      <- result as String: `Hello, ${name}`

bad/dev/tests.ek9

#!ek9
defines module error.e81010.bad.tests

  references
    error.e81010.bad::greeting

  defines program

    @Test
    GreetingOnce()
      stdout <- Stdout()
      stdout.println(greeting("EK9"))

bad/dev/expected_output.txt

Hello, {{UUID}}

$ ek9 -t greeting.ek9
ℹ️ Found 1 test:
  1 blackbox (output validated against expected_output.txt)

Executing 1 test...

❌ FAIL error.e81010.bad.tests::GreetingOnce [BlackBox] (nms)
    E81010: Invalid placeholder(s) in expected output: UUID

Summary: 0 passed, 1 failed (1 total)
Types: 1 blackbox
Duration: nms
ek9: tests failed (exit 11)

Fixed: The placeholder is the EK9 type String

good/greeting.ek9

#!ek9
defines module error.e81010.good

  defines function

    greeting() as pure
      -> name as String
      <- result as String: `Hello, ${name}`

good/dev/tests.ek9

#!ek9
defines module error.e81010.good.tests

  references
    error.e81010.good::greeting

  defines program

    @Test
    GreetingOnce()
      stdout <- Stdout()
      stdout.println(greeting("EK9"))

good/dev/expected_output.txt

Hello, {{String}}

$ ek9 -t greeting.ek9
ℹ️ Found 1 test:
  1 blackbox (output validated against expected_output.txt)

Executing 1 test...

✅ PASS error.e81010.good.tests::GreetingOnce [BlackBox] (nms)

Summary: 1 passed, 0 failed (1 total)
Types: 1 blackbox
Duration: nms