Fix avg_cost to return per-share cost basis (#1692)

* Fix avg_cost to return per-share cost basis

* Revert "Fix avg_cost to return per-share cost basis"

This reverts commit 38c438a614.

* Normalize SimpleFIN holding cost basis

* Track SimpleFIN cost basis source field

* Add SimpleFIN cost basis normalization tests

* Update SimpleFIN value cost basis expectation

* Handle missing SimpleFIN quantity for cost basis

* Ignore missing SimpleFIN cost basis fields

* Fix SimpleFIN holdings processor test setup

test/models/simplefin_account/investments/holdings_processor_test.rb

@@ -0,0 +1,95 @@
+require "test_helper"
+
+class SimplefinAccount::Investments::HoldingsProcessorTest < ActiveSupport::TestCase
+  setup do
+    @processor = SimplefinAccount::Investments::HoldingsProcessor.new(nil)
+  end
+
+  test "cost_basis source is used unchanged as per share basis" do
+    payload = {
+      "cost_basis" => "16.61",
+      "total_cost" => "9588.61",
+      "value" => "10108.16"
+    }
+
+    raw_cost_basis, source_key = @processor.send(:cost_basis_from, payload)
+    cost_basis = @processor.send(:normalize_cost_basis, raw_cost_basis, BigDecimal("577.279"), source_key)
+
+    assert_equal BigDecimal("16.61"), cost_basis
+    assert_equal "cost_basis", source_key
+  end
+
+  test "basis source is used unchanged as per share basis" do
+    payload = {
+      "basis" => "16.61",
+      "total_cost" => "9588.61"
+    }
+
+    raw_cost_basis, source_key = @processor.send(:cost_basis_from, payload)
+    cost_basis = @processor.send(:normalize_cost_basis, raw_cost_basis, BigDecimal("577.279"), source_key)
+
+    assert_equal BigDecimal("16.61"), cost_basis
+    assert_equal "basis", source_key
+  end
+
+  test "total_cost source is normalized to per share basis" do
+    payload = {
+      "total_cost" => "9588.61"
+    }
+
+    raw_cost_basis, source_key = @processor.send(:cost_basis_from, payload)
+    cost_basis = @processor.send(:normalize_cost_basis, raw_cost_basis, BigDecimal("577.279"), source_key)
+
+    assert_equal BigDecimal("9588.61") / BigDecimal("577.279"), cost_basis
+    assert_equal "total_cost", source_key
+  end
+
+  test "value source is normalized to per share basis" do
+    payload = {
+      "value" => "9588.61"
+    }
+
+    raw_cost_basis, source_key = @processor.send(:cost_basis_from, payload)
+    cost_basis = @processor.send(:normalize_cost_basis, raw_cost_basis, BigDecimal("577.279"), source_key)
+
+    assert_equal BigDecimal("9588.61") / BigDecimal("577.279"), cost_basis
+    assert_equal "value", source_key
+  end
+
+  test "total cost source with zero quantity returns nil" do
+    payload = {
+      "total_cost" => "9588.61"
+    }
+
+    raw_cost_basis, source_key = @processor.send(:cost_basis_from, payload)
+    cost_basis = @processor.send(:normalize_cost_basis, raw_cost_basis, BigDecimal("0"), source_key)
+
+    assert_nil cost_basis
+    assert_equal "total_cost", source_key
+  end
+
+  test "total cost source with nil quantity returns nil" do
+    payload = {
+      "total_cost" => "9588.61"
+    }
+
+    raw_cost_basis, source_key = @processor.send(:cost_basis_from, payload)
+    cost_basis = @processor.send(:normalize_cost_basis, raw_cost_basis, nil, source_key)
+
+    assert_nil cost_basis
+    assert_equal "total_cost", source_key
+  end
+
+  test "missing cost basis fields return nil" do
+    payload = {
+      "market_value" => "10108.16"
+    }
+
+    raw_cost_basis, source_key = @processor.send(:cost_basis_from, payload)
+    cost_basis = @processor.send(:normalize_cost_basis, raw_cost_basis, BigDecimal("577.279"), source_key)
+
+    assert_nil raw_cost_basis
+    assert_nil source_key
+    assert_nil cost_basis
+  end
+end