Refactor testFFT (#242)

* Moved the block of code to a clearly named test.

* Clarified the name of the temporary variable.

* Clarified the name of the temporary variable.

* Clarified the name of the temporary variable.

* Formatted the test to follow the arrange, act and assert form.

* Grouped the assertions together.

* Extracted a computation to an intention-revealing temporary variable.

* Clarified the name of the test.

* Extracted block of test code to a clearly named test method.

* Removed obsolete code.

* Clarified the name of the test.

* Formatted the test to follow the arrange, act and assert form.

* Improved the name of the temporary variable.

* Copied block of test code to a clearly named test method.

* Removed obsolete, duplicated code.

* Formatted the test to follow the arrange, act and assert form.

* Improved the names of the test messages.

* Clarified the name of the temporary variable.

* Made similar code even more similar.

* Made similar code even more similar.

* Extracted duplicate code to an intention revealing message.

* Inlined the temporary variable.

* Made similar code even more similar.

* Made similar code even more similar.

* Made similar code even more similar.

* Replaced the use of a deprecated method.

* Clarified the name of the test message.

* Made the name of the test message more concise by an attempt to use the domain language (Wikipedia).

* Improved code formatting.

* Clarified the name of a temporary variable.

Author: hemalvarambhia

src/Math-FastFourierTransform/PMFastFourierTransform.class.st

@@ -14,7 +14,7 @@ Class {
 		'permTable',
 		'data'
 	],
-	#category : 'Math-FastFourierTransform'
+	#category : #'Math-FastFourierTransform'
 }
 
 { #category : #'instance creation' }
@@ -140,7 +140,7 @@ PMFastFourierTransform >> transformForward: forward [
 			[ :j | 
 			temp := self multiplier: (j - 1) * (n // lev).
 			forward
-				ifFalse: [ temp := temp conjugated ].
+				ifFalse: [ temp := temp complexConjugate ].
 			i := j.
 			[ i <= n ]
 				whileTrue:

src/Math-Tests-FastFourierTransform/PMFFTTest.class.st

@@ -4,6 +4,13 @@ Class {
 	#category : #'Math-Tests-FastFourierTransform'
 }
 
+{ #category : #tests }
+PMFFTTest >> generateCosineWaveSignal: sampleSize [
+
+	^ (1 to: sampleSize) collect: [ :i | 
+		  (Float pi * (i - 1) / (sampleSize / 8)) cos ]
+]
+
 { #category : #tests }
 PMFFTTest >> testBitReverse [
 	self should: [ 1 bitReverse: 0 ] raise: Error.
@@ -21,35 +28,63 @@ PMFFTTest >> testBitReverse [
 ]
 
 { #category : #tests }
-PMFFTTest >> testFFT [
-	| data data1 f s |
-	data := (1 to: 256)
-		collect: [ :i | (Float pi * (i - 1) / (256 / 8)) cos ].
-	f := PMFastFourierTransform data: data.
+PMFFTTest >> testFastFourierTransformCalculatesTheDiscreteFourierTransformWithoutLossOfSignalForLargeDataSets [
+
+	| inputSequence f zeroedImaginaryData inputOutputDiff zeroedRealData |
+	inputSequence := self generateCosineWaveSignal: 256.
+	f := PMFastFourierTransform data: inputSequence.
+
 	f transform.
 	f inverseTransform.
-	s := (f imaginaryData select: [ :i | i equalsTo: 0 ]) size.
-	self assert: s equals: 256.
-	s := (f realData - data select: [ :i | i equalsTo: 0 ]) size.
-	self assert: s equals: 256.
-	PMMitchellMooreGenerator reset: 1.
-	data1 := data collect: [ :i | i + 0.001 random - 0.0005 ].
-	f := PMFastFourierTransform data: data1.
+
+	zeroedImaginaryData := (f imaginaryData select: [ :i | i equalsTo: 0 ]) size.
+	inputOutputDiff := f realData - inputSequence.
+	zeroedRealData := (inputOutputDiff select: [ :i | i equalsTo: 0 ]) size.
+	self assert: zeroedImaginaryData equals: 256.
+	self assert: zeroedRealData equals: 256.
+
+	PMMitchellMooreGenerator reset: 1
+]
+
+{ #category : #tests }
+PMFFTTest >> testFastFourierTransformCalculatesTheDiscreteFourierTransformWithoutLossOfSignalForSmallDataSets [
+
+	| inputSequence f zeroedImaginaryData inputOutputDiff zeroedRealData |
+	inputSequence := #( -2 -2 -2 3 3 3 1 -2 ).
+	f := PMFastFourierTransform data: inputSequence.
+
+	f transform.
+	f inverseTransform.
+
+	zeroedImaginaryData := (f imaginaryData select: [ :i | i equalsTo: 0 ]) size.
+	inputOutputDiff := f realData - inputSequence.
+	zeroedRealData := (inputOutputDiff select: [ :i | i equalsTo: 0 ]) size.
+	self assert: zeroedImaginaryData equals: 8.
+	self assert: zeroedRealData equals: 8
+]
+
+{ #category : #tests }
+PMFFTTest >> testFrequencyDomainRepresentationMatchesRandomizedInputSignalClosely [
+
+	| cosineWaveSignal randomizedCosineWaveSignal f |
+	cosineWaveSignal := self generateCosineWaveSignal: 256.
+	randomizedCosineWaveSignal := cosineWaveSignal collect: [ :i | i + 0.001 random - 0.0005 ].
+	f := PMFastFourierTransform data: randomizedCosineWaveSignal.
+
 	f transform.
 	f chop: 0.01.
 	f inverseTransform.
-	self assert: (f realData - data) abs max < 4e-5.
-	data := #(-2 -2 -2 3 3 3 1 -2).
-	f := PMFastFourierTransform data: data.
+
+	self assert: (f realData - cosineWaveSignal) abs max < 4e-5
+]
+
+{ #category : #tests }
+PMFFTTest >> testThatChopSuccessivelyRemovesInputSignalPointsLowerThanTolerance [ 
+	| inputSignal f |
+	inputSignal := #(-2 -2 -2 3 3 3 1 -2).
+	f := PMFastFourierTransform data: inputSignal.
 	f chop: 1.01.
 	self assert: f realData equals: #(-2 -2 -2 3 3 3 0 -2).
 	f chop: 2.01.
 	self assert: f realData equals: #(0 0 0 3 3 3 0 0).
-	f data: data.
-	f transform.
-	f inverseTransform.
-	s := (f imaginaryData select: [ :i | i equalsTo: 0 ]) size.
-	self assert: s equals: 8.
-	s := (f realData - data select: [ :i | i equalsTo: 0 ]) size.
-	self assert: s equals: 8
 ]