diff --git a/test/unit/operation.js b/test/unit/operation.js
new file mode 100644
index 0000000..de2a12e
--- /dev/null
+++ b/test/unit/operation.js
@@ -0,0 +1,22 @@
+const o = require('../../src/operation')
+
+describe('Operation', function() {
+
+    it('op_prefix', function() {
+        o.op_prefix('arst').should.deep.equal({name: 'arst', operation: 'add'})
+        o.op_prefix('+arst').should.deep.equal({name: 'arst', operation: 'add'})
+        o.op_prefix('-arst').should.deep.equal({name: 'arst', operation: 'subtract'})
+        o.op_prefix('~arst').should.deep.equal({name: 'arst', operation: 'intersect'})
+        o.op_prefix('^arst').should.deep.equal({name: 'arst', operation: 'stack'})
+    })
+
+    it('operation', function() {
+        // without choices, it's the same as op_prefix
+        o.operation('arst').should.deep.equal({name: 'arst', operation: 'add'})
+        // with choices, it propagates type where it found the name
+        o.operation('arst', {bad: [], good: ['arst']}).should.deep.equal({name: 'arst', operation: 'add', type: 'good'})
+        // it also respects order when overridden
+        o.operation('arst', {first: ['arst'], second: ['arst']}, ['second', 'first']).should.deep.equal({name: 'arst', operation: 'add', type: 'second'})
+    })
+
+})
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